CONVERTING OLD TELEPHONES
TO THE UK PLUG AND SOCKET SYSTEM

Click here on where to obtain replacement braided telephone cords

UK cord wire colours to Non -UK cord wire colours converter

Click here for instructions on how to fit an electronic Transmitter and Rectifier Element No. 205

Click here to view a fully converted Telephone No. 706 and No. 746 - also applicable to all 700 type telephones

Click here on how to wire up sockets

Non UK phone to UK conversion

Onyx Telephones - Italian phones with a square circuit board inside

Basic fault finding on your telephone and issues after converting

Around 1979, Post Office Telephones introduced the Plug and Socket (PST) method of connection.  This document explains how to convert many old British telephone instruments to PST working.  The following information assumes that a standard new plan BT line cord (light grey, flat plastic (ridge on one flat) with a flat plug one end and spades the other) is used.  Do not attempt to fit a new style plug to the old style round PVC or cloth telephone line cord - this usually fails - buy the correct cord or similar.

From 2022 onwards there is a national conversion of all UK telephone lines to Voice Over IP working.  For those with old phones this means that dials may not work, as many providers are not supporting pulse dial signalling.  To allow old dial phones to continue working a pulse to tone converter must be purchased.  These are a simple plug in unit that will convert the dial pulses into tones, which is what the new system requires.  Click here for more information.

If your replacement cord has no grommet (grommets were only used on 700 type telephones) just slit the original grommet with a sharp knife, pull out the old cord, insert the new cord with a blob of glue and refit into phone.  The original 200 and 300 type telephone line cords were restrained by a cotton tie.  For these phones just insert the replacement line cord into the telephone and tie a knot in it (the latest replacement cords have grommets on them - these will stop the cable from pulling out).

Strap or Link
There are references to strapping and straps in the text below.  This refers to the metal links that connect two terminals together. They can be removed by releasing the screws that hold them captive - always tighten the screws again afterwards as they have a tendency to fall out. In some instances these straps are replaced by wire and in fact a strap can be a piece of wire.

Terminal Numbering
There are also references below to T and B numbers.  T1 would mean terminal 1 in the telephone, whilst B2 would mean terminal 2 in the Bellset.  Any other letters will be self evident.

The cord colours used by BT are shown below and are used throughout this page.  If you are not using a standard BT cord then click here.

BT Line Cord Colours are:- R = RED, W = WHITE, B = BLUE, G = GREEN

The conversions below assume that the original telephone line cord will be discarded and replaced with a modern line cord.

Converting an old GPO telephone does not make it approved and therefore it cannot be legally connected to any Telecom network in the UK.

Always fit a rectifier unit (Rectifier Element No. 205) across the earpiece of a converted telephone (these stop acoustic shock).  Click here for instructions.

As the original carbon granule transmitters are generally noisy or faint it is also advisable to change them to a modern electronic type (these are generally a direct replacement for 700 type transmitters and can be modified to fit in Bakelite handsets).  Click here for instructions.

For most UK non-GPO telephones the conversion information is on the relevant telephone page.

If your telephone does not appear in this list then please contact the author for conversion advice.
 

UK Telephone Conversions

GPO/PO/BT Telephone Conversions

GPO Telephone No. 1

Telephone is wired to standard diagram (N101). This telephone does not lend itself to proper conversion, but can be adapted as follows:-

1. Remove strap between terminals L1 and E and replace with a 3.3k ohm resistor.
2. White wire of new line cord to terminal L1.
3. Red wire of new line cord to terminal L2.
4. Green and blue wires of new line cord are insulated with tape (they are not used).

GPO Telephone No. 11

Telephone is wired to standard diagram (N111). This telephone does not lend itself to proper conversion, but can be adapted as follows:-

1. Remove strap between terminals G and EB and replace with a 3.3k ohm resistor.
2. White wire of new line cord to terminal A.
3. Red wire of new line cord to terminal B.
4. Connect two D type (U2) batteries in series and connect the positive of the batteries to the + terminal (red wire) and the negative of the batteries to the - terminal (red/white wire).  The D batteries should be fitted in a proper battery holder.  The batteries should be no more than 3 volts).
5. Blue wire of the new line cord to terminal G.
6. Remove the orange/white wire from terminal 3 of the generator.
7. Green wire of new line cord is insulated with tape (not used).

GPO Telephone No. 121

Telephone is wired to standard diagram (N221) but modified as follows:-

Telephone with numbered terminals:-

1. White wire of new line cord to terminal 4.
2. Remove strap between terminals 4 and 6 and insert a 3.3k ohm resistor  between terminals 4 and 6 (the link may a piece of wire soldered to the terminals).
3. Red wire of new line cord to terminal 8.
4. Blue wire of new line cord to terminal 3.
5. Disconnect one wire from the capacitor and insulate.
6. Green wire of new line cord - insulate with tape (not used).
7. Terminals 2 and 5 should be linked already - check on this.

1. Disconnect  the Green/white wire on the capacitor.
2. Connect the blue line cord wire to the green/white wire and insulate.
3. Remove the strap between L1 and E (this may be soldered under the terminal strip).
4. Insert a 3k3 resistor between L1 and E.
5. Connect the white line cord wire to L1.
6. Connect the red line cord wire to L2.
7. Insulate the green line cord wire.

GPO Telephone No. 150 with Bellset No. 1 or Bellset 25

Telephone is wired to standard diagram (N250) which includes the Bellset but modified as follows:-

1. Telephone cord - White - wired between terminal T in phone and terminal L2 in a Bellset No. 1.
2. Telephone cord - White - connect directly to Red of new line cord in a Bellset No. 25.  Use a small nut and bolt and then cover with insulation tape.
3. Telephone cord - Red - wired between terminal TR in phone and terminal TR in Bellset.
4. Telephone cord - Green - wired between terminal R in phone and terminal R in Bellset.
5. White wire of new line cord to terminal L1 in Bellset.
6. Remove strap between terminal L1 and terminal E and insert a 3.3k ohm resistor.
7. Remove the terminal T - L2 metal strap in the Bellset No. 1.  There is a soldered strap in a Bellset No. 25, behind the terminal plate, in this instance leave the strap in place.
8. Red wire of new line cord to terminal L2 in a Bellset No. 1.
9. Blue wire of new line cord to terminal T in Bellset.
10. Short out the two terminals of the capacitor with a piece of bare wire.
11. Green wire of new line cord - insulate with tape (not used).

To disconnect bell (if needed)
Remove strap between L1 and E or leave out the resistor.

Dial terminations
The dial on a Telephone No. 150 is wired as follows:-

• Dial terminal 1 to telephone terminal D using the blue wire of the dial cord.
• Dial terminal 2 to telephone terminal R using the grey wire of the dial cord.
• Dial terminal 3 to telephone terminal TS using the brown wire of the dial cord.
• Dial terminal 4 to telephone terminal TD using the pink wire of the dial cord.
• Dial terminal 5 to telephone terminal T using the orange wire of the dial cord.

GPO Telephone No. 151

Telephone is wired to standard diagram (N251).

This telephone is designed for use on Local Battery circuits and therefore a battery is used to power the transmitter.  A 3 volt battery should be connected inside the telephone in a battery holder (two D size or U2 batteries are suggested).

The phone is modified as follows:-

1. Remove link between 7 and 8.
2. Remove link between 11 and 12.
3. Terminals 1 and 2 must be linked.
4. Terminals 6 and 7 must be linked.
5. Red wire of new line cord to terminal 11.
6. Blue wire of new line cord to terminal 8.
7. White wire of new line cord to terminal 1.
8. Green wire of new line cord - insulate with tape (not used).
9. Positive of Battery to terminal 10.
10. Negative of battery to terminal 9.

GPO Telephone No. 156
Four Bellsets can be used on this telephone.  As Bellsets 21 and 31 require a battery, it is recommended to only connect using a Bellset No. 1 or 25.

Using Bellset No. 1 or Bellset No. 25
Telephone is wired to standard diagram (N256):-

1. Remove the link between Terminals 7 and 4 in the phone.
2. Telephone cord - White wire - wired between 2 in phone and L2 in a Bellset No. 1.
3. Telephone cord - White wire - connect directly to the Red wire of line cord in a Bellset No. 25.  Use a small nut and bolt and then cover with insulation tape.
4. Telephone cord - Red wire - wired between 3 in phone and TR in Bellset.
5. Telephone cord - Green wire - wired between 6 in phone and R in Bellset.
6. White wire of new line cord to L1 in Bellset.
7. Remove strap between L1 and E and insert a 3.3k ohm resistor.
8. Remove the T - L2 metal strap in the Bellset No. 1.  There is a soldered strap in a Bellset No. 25, behind the terminal plate, in this instance leave the strap in place.
9. Red wire of new line cord to L2 in a Bellset No. 1.
10. Blue wire of new line cord to T in Bellset.
11. Short out the two terminals of the capacitor with a piece of wire.
12. Green wire of new line cord - insulate with tape (not used).

To disconnect bell (if required)
Remove strap between L1 and E in the Bellset or leave out the resistor.

Using Bellset No. 21 or Bellset No. 31
Better to use a Bellset No. 1 or 25 as the Bellsets No. 21 and 31 will require a 3 volt (2 x 1.5volts plus a holder) battery.
The modification below is non-standard.
Telephone is wired to standard diagram (N256):-

1. In a Bellset No. 21 remove the link E and replace with a 3.3k ohm resistor.
2. In a Bellset No. 31 remove the link between terminals 6 and 7 and insert a 3.3k ohm resistor.
3. Telephone cord - White wire - wired between terminal 3 in phone and terminal 2 in Bellset.
4. Telephone cord - Red wire - wired between terminal 1 in phone and terminal 3 in Bellset.
5. Telephone cord - Green wire - wired between terminal 4 in phone and terminal 4 in Bellset.
6. Telephone cord - Orange wire - wired between terminal 2 in phone and terminal 1 in Bellset.
7. Telephone cord - Blue wire - wired between terminal 8 in phone and terminal 7 in Bellset.
8. White wire of new line cord to terminal 6 in Bellset.
9. Red wire of new line cord to terminal 8 in Bellset.
10. Blue wire of new line cord - insulate with tape (not used).
11. Green wire of new line cord - insulate with tape (not used).
12. Battery is connected to terminals 4 and 5 in the Bellset.

GPO Telephone No. 162

Telephone is wired to standard diagram (N262) which includes the Bellset No. 1 or 25 but modified as follows:-

1. Remove the wire link between T - L2, which is under the Bellset terminal board.
2. Telephone cord - White - goes from terminal 3 in phone to L2 in Bellset.
3. Telephone cord - Red - goes from terminal 1 in phone to TR in Bellset.
4. Telephone cord - Green - goes from terminal 2 in phone to R in Bellset.
5. If it exists, remove the wire strap/link between E and L1 in the Bellset and insert a 3.3k ohm resistor.
6. New line cord - White wire to L1 in Bellset.
7. New line cord - Red wire to L2 in Bellset.
8. New line cord - Blue wire to T in Bellset.
9. New line cord - Green wire - insulate with tape (this wire is not used).
10. Short out the two terminals of the capacitor (square grey box shaped object) in the Bellset by wrapping a wire between the terminals.
     

To disconnect bell (if required)
Remove strap between L1 and E or leave out the resistor.

GPO Telephone No. 1/196

Telephone is wired to standard diagram (N296) but reference to the full wiring diagram must be made for connection to a Bellset No. 31(N1297).
This telephone is designed for use on Local Battery circuits and therefore a battery is used to power the transmitter.  A 3 volt battery should be connected to the Bellset (two D size or U2 batteries are suggested).

Conversion using a Telephone No. 1/196 and Bellset No. 31 is as follows:-

1. Orange of cord between Telephone and Bellset - T2 connects to B1.
2. Green of cord between Telephone and Bellset - T4 connects to B5.
3. Red of cord between Telephone and Bellset - T1 connects to B4.
4. White of cord between Telephone and Bellset - T3 connects to B2.
5. Install Battery to Bellset terminals B4 and B3 with positive connected to B3.
6. Telephone line cord - White wire - to B6 in Bellset.
7. Telephone line cord - Red wire - to B8 in Bellset.
8. Telephone line cord - Blue wire -  to B1 in Bellset.
9. Telephone line cord - Green wire - not used so just insulate.
10. Remove one of the wires from the capacitor and insulate.
11. Insert a 3.3k resistor between B6 and B7 in the Bellset (these terminals may be linked by a soldered wire on the rear of the terminal block.  Remove this link if it exists.

GPO Telephone No. 221

Telephone is wired to standard diagram (N321) which includes the Bellset but modified as follows:-

Telephone with numbered terminals:-

1. Disconnect the green/white wire from the capacitor.
2. Connect the green/white to the blue wire of the line cord and insulate.
3. Remove the strap between terminals 6 and 7.
4. Insert a 3.3k resistor between terminals 6 & 7.
5. White wire of the line cord to terminal 6.
6. Red wire of the line cord to terminal 9.
7. Insulate green of the line cord as it is not used.

1. Disconnect and sleeve the Green wire that is on TR (it goes to terminal 2 of the Induction Coil and is not needed).
2. Move the Orange wire from the Condenser that is on L2 - onto TR.
3. Wire the Condenser tags together (square metal box).
4. Remove the strap between L1 and E (this may be soldered under the terminal strip).
5. Insert a 3k3 resistor between L1 and E.
6. Connect the white line cord wire to L1.
7. Connect the red line cord wire to L2.
8. Connect the blue line cord wire to TR.
9. Insulate green of the line cord as it is not used.

GPO Telephone No. 232

There are two variants of this telephone, the Mark 1 and the Mark 2.  There was a major change made in so much as the green wire of the handset cord was moved from terminal 6 to terminal 8.  If fitting a Rectifier Element No. 205 or restoring a telephone, then be mindful that the paster diagram inside the phone may not be the right one, so always check the wiring on the two terminals to unsure what Mark you have.
This can be done as follows:-
Mark 1 - Terminal 6 - green & Terminal 8 - yellow and black (Green of the handset connects to Terminal 6).
Mark 2 - Terminal 6 - yellow and black & Terminal 8 green (Green of the handset connects to Terminal 8).

If fitting a Rectifier Element No. 205, connect the device to terminals 5 & 6 on the Mark 1 and terminals 5 and 8 on the Mark 2.  You could connect the device to R and MR terminals of the handset, instead, if you so wish.

Telephone is wired to the standard diagram (N332) but modified as follows:-
(B = Bellset terminal & T = Telephone Terminal).

With Bellset No. 25 and using the original cloth cord between the telephone and Bellset.

1. Short out the two terminals of the capacitor (square grey box shaped object) in the Bellset by wrapping a wire between the terminals.
2. Ensure that Bellset strap T - L2 is removed (there maybe be a soldered link on the tags).
3. Insert a 3.3k ohm resistor between T and L2.
4. Wire the cords as per the table below.
5. Green of the line cord is not used - insulate with tape.

With Bellset No. 26 and using the original cloth cord between the telephone and Bellset.

1. Remove Bellset strap B4 - B5.
2. Remove Bellset strap B2 - B3.
3. Insert a 3.3k ohm resistor between B2 and B3.
4. Ensure that Bellset strap B7 - B8 is in place.
5. Wire the cords as per the table below.
6. Green of the line cord is not used - insulate with tape.

With Bellset No. 31 and using the original cloth cord between the telephone and Bellset.

1. Remove Bellset strap B6 - B7.
2. Connect 3.3k resistor between Bellset E and B9.
3. Wire the cords as per the table below.
4. Green of the line cord is not used - insulate with tape.

With Bellset No. 37 and using the original cloth cord between the telephone and Bellset.

1. Remove Bellset strap B7 - B8.
2. Connect 3.3k resistor between Bellset B7 and B8.
3. Wire the cords as per the table below.
4. Green of the line cord is not used - insulate with tape.

With Bellset No. 41 and using the original cloth cord between the telephone and Bellset.

1. Remove Bellset strap B8 - B9.
2. Remove Bellset strap B6 - B7.
3. Remove Bellset strap B2 - B4.
4. Connect 3.3k resistor between Bellset B5 and B8.
5. Wire the cords as per the table below.
6. Green of the line cord is not used - insulate with tape.

The table below advises of the cord termination

Telephone - Cord - Bellset - Line Cord

Without any Bellset and not using the original cloth cord between the telephone and Bellset (New style line cord directly connected phone).  See picture below.

1. Red of line cord to T3.
2. White of line cord to T1.
3. Blue of line cord to T2.
4. Green of line cord is not connected - insulate with tape.

GPO Telephone connected to a Bell No. 1

Any standard bell can be connected to a Telephone No. 232 as the telephone has an Induction Coil fitted.  Capacitors are not required in the telephone any more as one is fitted inside the master socket.

Bellset No. 1 terminals number left to right.
In the Bell No. 1 there is a metal link between terminals 2 and 3.  Remove the link and insert a 3.3k resistor in it's place.
Fit the Rectifier Element No. 205 - refer to the instructions in the German conversion below.
Now connect the telephone and the bell together as follows:-

GPO Telephone No. 232 for use in Germany

There are two variants of this telephone, the Mark 1 and the Mark 2.  There was a major change made in so much as the green wire of the handset cord was moved from terminal 6 to terminal 8.  If fitting a Rectifier Element No. 205 or restoring a telephone, then be mindful that the paster diagram inside the phone may not be the right one, so always check the wiring on the two terminals to unsure what Mark you have.
This can be done as follows:-
Mark 1 - Terminal 6 - green & Terminal 8 - yellow and black (Green of the handset connects to Terminal 6).
Mark 2 - Terminal 6 - yellow and black & Terminal 8 green (Green of the handset connects to Terminal 8).

If fitting a Rectifier Element No. 205, connect the device to terminals 5 & 6 on the Mark 1 and terminals 5 and 8 on the Mark 2.  You could instead connect the device to the R and MR terminals in the handset if you so wish.

There are two plugs used in Germany, the TAE plug and the RJ45 plug.  As the German system only uses two wires then the line cord can be fitted with any of the two plugs, but at the phone end the wires will have to be fitted with spade connectors. 

The instructions below use a cloth 3 way cord between the Telephone and the Bellset and a line cord with a German plug on the end.  The bells may require adjusting as the ringing current is not the same as the UK.

1. Red wire of cloth cord is connected between Telephone terminal 1 and Bellset terminal 1.
2. White wire of cloth cord is connected between Telephone terminal 3 and Bellset terminal 5.
3. Green wire of cloth cord is connected between Telephone terminal 2 and Bellset terminal 3.
4. Ensure that Bellset terminal straps/links 7-8, 2-3 and 5-4 are in place.
5. Connect one wire of the German Plug ended line cord to Bellset Terminal 7.
6. Connect the other wire of the German Plug ended line cord to Bellset Terminal 5.
7. Connect a Rectifier Element No. 205 as per the instructions above.

GPO Telephone No. 246

The standard diagram for the Phone is N326 and the wiring Diagram for the phone and Bellset No. 37 is N4299.  (B = Bellset terminal & T = Telephone Terminal).

Telephone is wired as follows:-

1. Connect red wire of line cord to B6.
2. Connect white wire of line cord to B8.
3. Connect blue wire of line cord to BE.
4. B8 wired to T8.
5. B1 wired to T9.
6. If no dial is fitted then connect a wire to B6, B4 and T7.
7. B9 wired to T2.
8. BE wired to T1.
9. B3 wired to T6.
10. B2 wired to T5.
11. Remove the soldered wire link between B7 and B8 - it is under the board.
12. Connect a 3.3k resistor between B7 and B8 (leave out if bell not to be connected).
13. Remove the white wire from Capacitor and insulate the end.
14. Insulate green wire of the line cord as it is not used.

If dial is fitted:-

1. Remove link between B4 and B6.
2. Leave T7 wired to B4.
3. Dial 1 and Dial 3 terminals to B5.
4. Dial 2 to B1.
5. Dial 4 to B4.
6. Dial 5 to B6.

GPO Telephone No. 248 and Bellset No.39A

This method of wiring is only applicable for the base unit and no extension phones may be wired from the Bellset.  The Bellset switch should be left in the speak to exchange position.  There are no bells for incoming calls in any of these Bellsets.  A bell was always fitted externally to the Bellset.  This could be a Bell No. 1, 59 or a Bellset No. 26.  If a bell is required then either fit it adjacent to the extension wall socket and wire it to tags 3 and 5 on the back of the wall socket or use a line cord to connect to the socket.  A 3.3k ohm resistor should also be fitted.

Telephone and Bellset are wired to follows (no bells are fitted):-

1. T3 to B19 and B20 - black of connecting cord.
2. T9 to B23 and B24 - pink of connecting cord.
3. T10 to B17 - brown of connecting cord.
4. T11 to B16 - grey of connecting cord.
5. T1 to B15 - blue of connecting cord.
6. Remove link B13 to B14.
7. Move the orange of connecting cord from B18 to B14 - the other end is connected to T2.
8. Blue wire of the line cord to B14.
9. White wire of the line cord to B1.
10. Red wire of the line cord to B3 and B4.
11. Insulate green wire of the line cord as it is not used.

GPO Telephone No. 248 and Bellset No.44

Telephone and Bellset are wired to follows (no bells are fitted):-

1. T3 to B34 and B35 - black of connecting cord.
2. T9 to B31 - pink of connecting cord.
3. T10 to B26 - brown of connecting cord.
4. T11 to B25 - grey of connecting cord.
5. T1 to B19, B20 and B21 - blue of connecting cord.
6. Remove any links between B13 and B14.
7. Remove any links between B17 and B18.
8. Move the orange of connecting cord to from B27 to B14 - the other end is connected to T2.
9. Blue wire of the line cord to B14.
10. White wire of the line cord to B1 and B2.
11. Red wire of the line cord to B3 and B4.
12. Green wire of the line cord - insulate - not used.

GPO Telephone No. 306

Telephone is wired as follows. The standard diagram is N406.

1. Remove strap T10 - T11.
2. Remove any wire or straps connected to T2, T3, T7, T12 or T13.
3. Do not fit a 3.3K ohm resistor as this telephone does not have a magneto bell.
4. Insert strap T8 - T9.
5. Red wire of line cord to T8.
6. White wire of line cord to T1.
7. Blue wire of line cord to T11.
8. Green wire of the line cord is spare and can be parked on T7.
9. Rectifier No. 205 (if needed) inserted between T6 & T5.

GPO Telephone No. 308

Telephone is wired as follows. The standard diagram is N408.

1. Remove strap T10 - T11.
2. Strap T11 - T12.
3. Install a 3.3K ohm resistor between T1 and T2.
4. Strap T8 - T9.
5. Red wire of line cord to T8.
6. White wire of line cord to T1.
7. Blue wire of line cord to T11.
8. Green wire of the line cord is spare and can be parked on T7.
9. Rectifier No. 205 (if needed) inserted between T6 & T5.

GPO Telephone No. 310

Telephone is wired as follows. The standard diagram is N410.

1. Remove strap T10 - T11.
2. Strap T11 - T12.
3. Install a 3.3K ohm resistor between T1 and T2.
4. Insert strap T1 - T9.
5. Red wire of line cord to T8.
6. White wire of line cord to T1.
7. Blue wire of line cord to T11.
8. Green wire of the line cord is spare and can be parked on T7.
9. Rectifier No. 205 (if needed) inserted between T6 & T5.

GPO Telephone No. 311

Telephone is wired as follows. The standard diagram is N411.

1. Remove strap T10 - T11.
2. Insert strap T11 - T12.
3. Install a 3.3K ohm resistor between T1 and T2.
4. Insert strap T1 - T7.
5. Red wire of line cord to T8.
6. White wire of line cord to T1.
7. Blue wire of line cord to T11.
8. Green wire of the line cord is spare and can be parked on T3.
9. Rectifier No. 205 (if needed) inserted between T6 & T5.

GPO Telephone No. 312

Telephone is wired as follows. The standard diagram is N412.

1. Remove strap T10 - T11.
2. Remove strap T12 - T13.
3. Insert a 3.3K ohm resistor between T11 & T12.
4. Link all the following terminals together T1 - T2.
5. Red of line cord to T8.
6. White of line cord to T1.
7. Blue of line cord to T11.
8. Green of the line cord is spare and can be parked on T7.
9. Rectifier No. 205 (if needed) inserted between T6 & T5.

GPO Telephone No. 314

Telephone is wired as follows. The standard diagram is N414.

1. Remove strap T10 - T11.
2. Remove strap T12 - T13.
3. Connect a 3.3K ohm resistor between T11 and T12.
4. Link terminals T2 and T7 together with a piece of wire.
5. Red wire of line cord to T8.
6. White wire of line cord to T7.
7. Blue wire of line cord to T11.
8. Green wire of the line cord is spare and can be parked on T9.
9. Rectifier No. 205 (if needed) inserted between T6 & T5.

Bell On/Off switch - Please refer to Diagram N4301 for additional information.
There are many types of key switches that could be used so check the number of the key switch unit and wire accordingly:-

1. Remove all key switch unit wires from the telephone terminals.
2. Wire the phone as above, but omit the link between T7 - T2.
3. On Key No's 302A and 302B, using the locking rotating switch, connect red wire from the switch to T7 and the green wire from the switch to T2.
4. On a Key No. 303A, with the the left hand key that locks down, connect switch terminal 27 to T7 (with a piece of wire) and also switch terminal 25 to T2 (with a piece of wire).
5. On a Key No. 304A, with the the left hand key that locks down, connect switch terminal 10 to T7 (with a piece of wire) and also switch terminal 12 to T2 (with a piece of wire).
6. On a Key No. 304B, with the the left hand key that locks down, connect switch terminal 11 to T7 (with a piece of wire) and also switch terminal 12 to T2 (with a piece of wire).
7. Insulate any other wires from the switch that cannot be easily removed.

GPO Telephone No. 321

Telephone is wired as follows. The standard diagram is N421.  If this telephone is wired with a switch, Thermistor and diode then remove these items and follow the instructions below.

1. Remove strap T10 - T11.
2. Remove strap T12 - T13.
3. Install a 3.3K ohm resistor between T12 and T13.
4. Strap T1 - T2 - T8 - T7.
5. Red wire of line cord to T3.
6. White wire of line cord to T1.
7. Blue wire of line cord to T11.
8. Green wire of the line cord is spare and can be parked on T9.
9. Rectifier No. 205 (if needed) inserted between T6 & T5.

GPO Telephone No. 326

Telephone is wired as follows. The standard diagram is N426.
This telephone has a DC ringer that will NOT work on an exchange line, so your phone will not ring.

1. Remove strap T10 - T11.
2. Remove any wire or straps connected to T2 or T12.
3. Do not fit a 3.3K ohm resistor as this telephone does not have a magneto bell.
4. Insert strap T8 - T9.
5. Red wire of line cord to T8.
6. White wire of line cord to T1.
7. Blue wire of line cord to T11.
8. Green wire of the line cord is spare and can be parked on T7.
9. Rectifier No. 205 (if needed) inserted between T6 & T5.

GPO Telephone No. 327

Telephone is wired as follows. The standard diagram is N427.

1. Remove strap T10 - T11.
2. Remove any wire or straps connected to T2 or T12.
3. Do not fit a 3.3K ohm resistor as this telephone does not have a magneto bell.
4. Insert strap T8 - T9.
5. Red wire of line cord to T8.
6. White wire of line cord to T1.
7. Blue wire of line cord to T11.
8. Green wire of the line cord is spare and can be parked on T7.
9. Rectifier No. 205 (if needed) inserted between T6 & T5.

GPO Telephone No. 328

Telephone is wired as follows.  The standard diagram is N428.

1. Remove strap T10 - T11.
2. Insert strap T8 - T9.
3. Insert strap T1 - T2.
4. Insert a 3.3K ohm resistor between T11 & T12.
5. Red wire of line cord to T9.
6. White wire of line cord to T1.
7. Blue wire of line cord to T11.
8. Green wire of the line cord is spare and can be parked on T7.
9. Rectifier No. 205 (if needed) inserted between T6 & T5.

Bell On/Off switch - Please refer to Diagram N4301 for additional information.

Bell switch not needed - phone will always ring

1. Remove all switch wires from the telephone terminals and insulated with tape.  Wire telephone as above.

Bell switch needed - switch will disconnect bell from ringing - there are many types of switches that could be used so check the number of the switch unit and wire accordingly.

1. Remove all switch wires from the telephone terminals.
2. Wire the phone as above, but omit the strap between T1 - T2.
3. Generic instructions - Connect one wire of switch to T1 and the other wire of switch to T2.
4. On Key No's 302A and 302B, with the locking rotating switch, connect red wire from the switch T1 and the green wire from the terminal to T2.
5. On a Key No. 303A, with the the left hand key that locks down, connect with wire switch terminal 27 to T1 and switch terminal 25 to T2.
6. On a Key No. 304A, with the the left hand key that locks down, connect with wire switch terminal 10 to T1 and switch terminal 12 to T2.
7. On a Key No. 304B, with the the left hand key that locks down, connect with wire switch terminal 11 to T1 and switch terminal 12 to T2.
8. Insulate any other wires from the switch from the switch that cannot be removed

GPO Telephone No. 330, 332 & 333

Telephone is wired as follows.  The standard diagrams are N430, N432 & N433.

1. Remove strap T10 - T11.
2. Remove strap T11 - T12.
3. Insert strap T8 - T9.
4. Insert strap T1 - T2.
5. Insert a 3.3K ohm resistor between T11 and T12.
6. Rectifier No. 205 (if needed) inserted between T6 & T5.
7. Red wire of line cord to T9.
8. White wire of line cord to T1.
9. Blue wire of line cord to T11.
10. Green wire of line cord to T3.

GPO Telephone No. 394

This is a special telephone and only works with local 3 volt battery.  To this end the phone cannot be wired exactly to UK standards and because of this you may find that when this phone dials out, other phones in the house tinkle.  It is suggested that two AA batteries be fitted inside the telephone.  The standard diagram is N494.

1. Insert a strap between T6 and T7.
2. Insert a 3.3K ohm resistor between T1 and T2.
3. Rectifier No. 205 (if needed) inserted between T6 & T5.
4. Red wire of line cord to T11.
5. White wire of line cord to T1.
6. Blue wire of line cord to T6.
7. Green wire of line cord to T3.
8. Battery to T10.
9. Battery to T9.

GPO Telephone No. 399

Telephone is wired as follows.  The standard diagram is N499.

1. Remove the original line cord.
2. Remove strap T10 - T11.
3. Remove strap T11 - T12.
4. Remove strap T8 - T9.
5. Insert strap T1 - T2.
6. Insert a 3.3K ohm resistor between T11 and T12.
7. Rectifier No. 205 (if needed) inserted between T6 & T5.
8. Red wire of line cord to T8.
9. White wire of line cord to T1.
10. Blue wire of line cord to T11.
11. Green wire of line cord to T3.

GPO Telephone No. 705

This is a coinbox which can be fitted with a Bellset No. 47 or a Bellset No. 49A.  As such these cannot be used as they were intended for, as the money chutes were controlled from the exchange.  They can be used to accept calls and the internal bell will ring..  The standard diagram is N805.  The "T" terminals are on the Bellset and the "B" terminals are on the backplate.  Some straps will already be in place.

Using the Bellset No. 47.

1. Insert a strap between terminals B11 and B12.
2. Insert a 3.3K ohm resistor between B2 and B8.
3. Remove the strap B1 to B9.
4. Red wire of line cord to B1.
5. White wire of line cord to B2.
6. Blue wire of line cord to B11 & B12.
7. Green wire of line cord B17.

Using the Bellset No. 49A.

1. Insert a strap between terminals T6 and T7.
2. Insert a strap between terminals T16 and T17.
3. Insert a 3.3K ohm resistor between B2 and B8.
4. Remove the strap B1 to B9.
5. Red wire of line cord to B1.
6. White wire of line cord to B2.
7. Blue wire of line cord to B11 & B12.
8. Green wire of line cord B17.

GPO Telephone No. 706, 710, 741 & 746

Telephone is wired as follows. The standard diagrams are (N806, N810, N841 & N846).

The bell or ringing device should be 4000 ohms resistance.  This can be rectified by either fitting the correct ringer or by inserting a 3.3K resistor in series with the ringer.  The telephone should already be fitted with a Rectifier No. 205.  If one is not fitted then it is recommended that one is fitted.

1. Remove strap T6 - T7.
2. Remove strap T4 - T5.
3. Insert strap T5 - T6.
4. Red wire of line cord to T8.
5. Blue wire of line cord to T6.
6. Insert straps T16 - T17 - T18 - T19.
7. White wire of line cord to T18.
8. Green wire of line cord to T15.
9. Insert a 3.3K resistor between T4 - T5 (object with coloured stripes on it).
10. Insert a Rectifier No. 205 (if needed) between T1 and T2.

The original BT line cord is called a Cord Connecting No 4/502

Bell On/Off switch
To fit a bell on/off switch obtain and fit the following items:-
(746 style phones need 2 pins, On/Off button and Switch No. 23A, whilst 706 style phones need Switch No. 5A and the appropriate coloured On/Off button).

Wire and install as follows:-

1. Remove strap T16 - T17 only.  Leave T17-T18 and T19 in place with the white of the line cord.
2. Connect Brown wire of switch to T16.
3. Connect Grey and Blue wires of the switch to T17.

Telephone No. 706 switch installation

1. Remove plastic blank plate from top of telephone case, by sliding the metal clip to one side.
2. Remove one of the screws that fixes the switch to the bracket.
3. Slacken off the other screw.
4. Slide the bracket round so that the plastic button can locate between the switch and the bracket.
5. Slide the switch back into position and insert the screws.
6. Fit the switch to the phone by first ensuring that the fixing screw is unscrewed at least 3/8th inch.
7. Then offer the switch to the phone at an angle and engage the lug.
8. Drop the other end of the switch down and fix by means of the single screw.

Telephone No. 710, 740 and 746 switch installation

1. Remove plastic blank plate from top of telephone case by pushing outwards from inside the case.
2. Offer the button into the opening so that the slots in button line up with slots inside casing.
3. Insert one pin so that it goes through the button and rests on the two slots inside the case.
4. Push the pin into the slots.
5. Repeat steps 3 & 4 for the other pin.
6. The switch is located centrally between the switch hooks.
7. Install the white nylon spring plunger by firstly pushing it down against the spring into the middle slot between the switch hooks.
8. Whilst depressing the plunger push towards the front of the phone until the triangular lug locates in the vertical slot.
9. Release the plunger and it rise slightly and then stop.
10. Then locate the switch, over the plunger and to one side, with the lug towards the front of the phone and just above the metal work.
11. Whilst pushing the switch against the white plunger, slide the switch down until the bottom locates into the bottom of the switch hook mounting and the lug at the top locates in the top of the mounting.
12. The white plunger can now be depressed.  It should operate the switch with an audible click and then spring back by itself.

GPO/PO Telephone 722, 766 & 786 (Trimphone)

Telephone is wired as follows. The standard diagrams are (N822, N866 & N886).

The bell or ringing device should be 4000 ohms resistance.  This is achieved by inserting a 3.3K resistor between T4 & T5.  It is sometimes preferable to not wire a Trimphone ringer up.  This is because it can sometimes upset the rest of your telephone ringers.  The Trimphone volume control has an Off position, which is obtainable by removing the case and slackening off the screw on top of the volume control switch itself.

1. Remove strap between terminals T6 - T7.
2. Remove strap between terminals T4 - T5.
3. Insert strap between terminals T5 - T6.
4. Connect red wire of line cord to terminal T8.
5. Connect blue wire of line cord to terminal T6.
6. Insert straps between terminals T16 - T17 - T18 - T19.
7. Connect white wire of line cord to terminal T18.
8. Connect green wire of line cord to terminal T15.
9. Insert a 3.3K resistor between terminals T4 - T5.

The original BT line cord is called a Cord Connecting No 4/504.

GPO/PO Telephone 745

Telephone is wired as follows. The standard diagram is N845.

The bell or ringing device should be 4000 ohms resistance.  This can be rectified by either fitting the correct ringer or by inserting a 3.3K resistor in series with the ringer.  The telephone should already be fitted with a Rectifier No. 205.  If one is not fitted then it is recommended that one is fitted.  If no dial is fitted then terminals T9 - T10 should be linked.

1. Remove strap between terminals T6 - T7.
2. Remove strap between terminals T4 - T5.
3. Insert strap between terminals T5 - T6.
4. Red wire of line cord to terminal T8.
5. Blue wire of line cord to terminal T6.
6. Insert straps between terminals T16 - T17 - T18 - T19.
7. White wire of line cord to terminal T18.
8. Green wire of line cord to terminal T15.
9. Insert a 3.3K resistor between terminals T4 - T5.
10. Insert a Rectifier No. 205 (if needed) between terminals T1 and T2.

The original BT line cord is called a Cord Connecting No 4/502

GPO/PO Telephone 776 (Compact) and Jubilee Compact

Telephone is wired to standard diagram (N876) but modified as follows:-

Telephone No. 776 and Jubilee without Bellset

1. Remove strap between terminals T2 - T3.
2. Insert strap between terminals T1 - T2.
3. Blue wire of line cord to terminal T1.
4. Red wire of line cord to terminal T4.
5. White wire of line cord to terminal T5.
6. Green wire of line cord to terminal T6.

Telephone No. 776 with Bell Unit No. 776 (using original cord between Telephone and Bellset)

1. Remove strap between terminals T2 - T3.
2. Insert strap between terminals T1 - T2.
3. Insert strap between terminals B1- B2 - B3.
4. Remove strap between terminals B5 - B6.
5. Insert 3.3k resistor between terminals B5 and B6.
6. Connect the cords as detailed in the table below (any colours in the original cord not mentioned below should be not used and insulated with tape.

Jubilee and Telephone SA4271 with Bellset Bell Unit SA4271 (using original cord between Telephone and Bellset).

In the instructions below the T refers to the telephone terminals 1 to 9.  Please disregard the handset terminals T1 & T2.

1. Bellset terminals L1, L2 and E are not used in these instructions and nothing should be connected to them.
2. Remove strap T2 - T3.
3. Insert strap T1 - T2.
4. Ensure that no strap exists between terminals B2 and B3.
5. Insert straps between terminals B5 - B6 - B7.
6. Remove strap between  terminals B3 - B4.
7. Insert 3.3k resistor between terminals B3 and B4.
8. Connect the cords as detailed in the table below.

GPO/BT TELEPHONE SPECIAL RANGE (TSR)

This telephone is based on the Telephone Unit D93458.  This is also used on the Telephone No. 776 (Refer to diagram N876).

1. Remove black and grey wire links (if they exist).
2. Remove the link between terminals 2 and 3.
3. Link terminals 1 and 2.
4. Connect one wire of the ringer to terminal 1.
5. Connect other wire of the ringer to terminal 7.
6. Connect 3.3k resistor between terminals 5 and 7.
7. Connect the white wire of the line cord to terminal 5.
8. Connect the red wire of the line cord to terminal 4.
9. Connect the blue wire of the line cord to terminal 2.
10. Connect the green wire of the line cord to terminal 6.

Notes:

1. Remove existing line cord.
2. Cut off grommet from new cord 4/502.
3. Connect new cord 4/502 to terminals as shown above and secure cord.
4. Fit a Thermistor 1A-1 between terminals 1 & 4 (if no terminal 4 appears on PCB then the Thermistor should be fitted between terminals G & Y).

Old method - not recommended

Notes:

1. Remove existing line cord and connect new Cord 4/502 to terminals as shown above.
2. Secure new cord and fit Thermistor 1A-1 between terminals 2 & 5.
   

Notes:

1. Remove existing cord.
2. Remove grommet from new cord 4/502 and connect as shown above.
3. Link W to the point below marked X.
4. Secure new cord.
   

Notes:

1. Remove existing line cord and remove grommet.
2. Remove the ends of the spade connectors on new Cord 4/502.
3. Solder the stumps to the TSR terminals as shown above.
4. Secure new cord 4/502 by modification of existing grommet.
5. Solder a Thermistor 1A-1 to terminals 3 & 4.
6. Insulate green and blue wires of the line cord as they are not used.
   

Notes:

1. Remove existing line cord and remove grommet.
2. Remove grommet from new Cord 4/502 and connect to terminals as shown above.
3. Secure line cord internally by re-utilisation of existing grommet.
4. Fit a Thermistor 1a-1 between terminals 17 & 18.
   

Notes:

1. Remove existing line cord.
2. Remove grommet from new cord 4/502 and connect to terminals as shown above.
3. Secure new cord internally.

The transmitter wires connect to terminals 8 and 9.

This telephone is based on the Telephone Unit D93458.  This is also used on the Telephone No. 776 (Refer to diagram N876).

1. Remove black and grey wire links (if they exist).
2. Remove the link between terminals 2 and 3.
3. Link terminals 1 and 2.
4. Connect one wire of the ringer to terminal 1.
5. Connect other wire of the ringer to terminal 7.
6. Connect 3.3k resistor between terminals 5 and 7.
7. Connect the white wire of the line cord to terminal 5.
8. Connect the red wire of the line cord to terminal 4.
9. Connect the blue wire of the line cord to terminal 2.
10. Connect the green wire of the line cord to terminal 6.

Other GPO Apparatus

GPO/PO Bellset No. 20

Using the Bellset with no telephones (bell only)

1. The switch on the Bellset must be set to "Speak to Exchange".
2. Remove the strap between the bell E and B terminals.
3. Connect a 3.3k resistor between E and B terminals.
4. Connect the white wire of line cord Terminal A.
5. Connect the blue wire of the line cord to Terminal E.
6. Insulate the terminals on the red and green wires of the line cord as these are not used.

Using the Bellset No. 20 with a Telephone No. 232
It is an onerous job to wire this setup and it may be more beneficial to wire the Telephone No. 232 separately to the Bellset and then connect the two with a doubler plug at the socket.

In this case convert the Telephone No. 232 as per the instructions on this page.

Convert the Bellset as shown above.

LOUDSPEAKING TELEPHONE No. 4D (Diagram N4475)

This telephone is powered by a 50 volt DC power supply.  It is not allowable to wire this via the line jack.  On the end of the LST line cord fit a six way junction box - the phone was originally fitted with a Block Terminal No. 36A.  Connect a new style line cord and the power supply to this junction box.

1. Remove strap T8 - T9.
2. Remove strap T4 - T5.
3. Red wire of old line cord to T8.
4. Blue wire of old line cord to T6.
5. Insert straps T16 - T17 - T18 - T19.
6. White wire of old line cord to T18.
7. Green wire of line cord to T13.
8. Insert a 3.3K resistor between T4 - T5.
9. + terminal connects the orange wire of the old line cord.
10. - terminal connects to the black wire of the old line cord.
11. In the junction box, connect the red wire of the old cord to the red wire of the new line cord.
12. In the junction box, connect the white wire of the old cord to the white wire of the new line cord.
13. In the junction box, connect the blue wire of the old cord to the blue wire of the new line cord.
14. In the junction box, connect the green wire of the old cord to the green wire of the new line cord.
15. In the junction box, connect the orange wire of the old cord to the positive terminal of the power unit.
16. In the junction box, connect the black wire of the old cord to the negative terminal of the power unit.
17. Ensure that the power wires do make contact with any other wires.

GPO/PO Planset N625

There are two wiring methods for connecting a Planset.  Method 1 is for a Planset with no extensions fitted to the Planset.  Method 2 is when extensions are connected to the Planset.

Method 1
These instructions are for the Planset only (i.e. with no extensions wired to the Planset).

These instructions assume that the Planset and attached phone are correctly wired to diagram N4509 already.

1. Red wire of the line cord to Block terminal 4.
2. White wire of the line cord to Block Terminal 6.
3. Blue wire of the line cord to Block terminal 5.
4. Replace the link between Planset terminals 6 and 7 with a 3.3k resistor.
5. In the telephone remove the capacitor connected to terminals 13 and 14.
6. In the telephone remove the link between terminals 6 and 7.
7. In the telephone link terminals 4, 5 and 6 together.  Leave any connected wires on these terminals.
8. In the telephone connect a piece of wire to Terminal 5 and run this wire into the Planset base. You will have to slacken or remove the three screws that fix the telephone to the base, so that the wire can be fed through.
9. In the Planset base remove the cord wire from Terminal 5. It should be orange/white in colour.
10. Connect the wire that was run in 8 above, to the orange/white cord wire and insulate.

Method 2
These instructions are used when the Planset has extensions wired to it.  Do not use Method 1.

The extensions should be wired, as normal, directly to the Planset Block Terminal.  This is not a pure conversion and you may find that when dialling out other phones connected to PST sockets tinkle.

1. Wire the Planset and extension phones together as per the relevant diagram (N4507 or N4509).
2. Red wire of the new line cord to Block terminal 4.
3. White wire of the new line cord to Block Terminal 6.
4. Insulate the Blue and Green wires of the new line cord as they are not used.

Non UK Telephone Conversions

The phones below are listed in alphabetical order depending on Manufacturers Name.  The line cord replacement in all the conversions below is the UK PST cord with the flat white plug.

AEP TIPO 332 (Click here for the diagram C110020)
Portuguese produced Telephone 332 made under licence.  The circuit is similar to the GPO Telephone No. 332.  The telephone wired to the diagram shown above does not have an internal bell fitted, the phone connects to an external Bellset.

1. Remove the existing line cord.
2. Link terminals T8 and T9.
3. Link Terminals T11 and T12.
4. Connect the red wire of the new line cord to terminal T8.
5. Connect the white wire of the new line cord to terminal T1.
6. Connect the blue wire of the new line cord to T11.
7. Connect a Rectifier Element to T5 and T6.
8. Insulate with tape the green wire of the new line cord.

Autophon Wandstation Model 50 (1950) (click here for the diagram)

There are two ways to convert this model telephone.  Try the first method and see if the bell rings.  If not then use the second method.

Method 1

1. Remove original line cord.
2. Remove any link between W1 and W2 terminals.
3. Insert a 3.3K ohm resistor between W1 and W2 terminals.
4. Connect the red wire of the new line cord to terminal a.
5. Connect the white wire of the new line cord to terminal  b.
6. Insulate with tape the blue and green wires of the new line cord (they are unused).

Method 2

1. Remove original line cord.
2. Remove any link between W1 and W2 terminals.
3. Insert a 3.3K ohm resistor between W1 and W2 terminals.
4. Connect the red wire of the new line cord to terminal a.
5. Connect the white wire of the new line cord to terminal  b.
6. Locate the capacitor with MF 1 stamped on it.  It is one of the three oblong objects to the right of the bell ringer (probably to upper one).
7. Locate the blue/white wires connected to this capacitor and disconnect them from the capacitor.
8. Join both blue/white wires to the blue line cord wire and insulate with tape.
9. Insulate with tape the green wire of the new line cord (it is unused).

Bell Princess
The US Princess telephone does not have an internal bell as it would not fit inside the case.  This is a basic conversion and bell tinkle in other telephones may occur.  Plug in bell ringers can be purchased in the UK.

1. Remove the existing line cord.
2. Connect the red wire of the new line cord to terminal L2.
3. Connect the white wire of the new line cord to terminal L1.

Bell Manufacturing Co. Kettle Phone

These phones have numerous diagrams.  Click here for conversion details

Bell Manufacturing Co. Model 2724
Click here for conversion information
 

Bell Manufacturing Co. Model 2725 - Diagram ST132 (Click here for diagram ST132)

1. Remove original line cord.
2. Red wire of the line cord to terminal B.
3. Remove the link between terminals A and S.
4. Insert 3.3k resistor between terminals A and S.
5. White wire of the line cord to terminal A.
6. Remove the single wire (sometimes two wires on some phones) from the 1uf capacitor (grey metal canister).  These wires are be on the terminal nearest the base plate.
7. Connect blue wire of the line cord to the wire that has just been removed and insulate.
8. Insulate the green wire of the line cord.

Bell Manufacturing Co. Model 2725 - Diagram BP10959 (Click here for diagram BP10959)

1. Remove the old line cord.
2. Remove the strap between terminals L1 and E.
3. Connect 3.3k resistor between terminals L1 and E.
4. Red wire of line cord to terminal L2.
5. White wire of line cord to terminal L1.
6. Green wire of line cord is spare and should be insulated.
7. Remove the red wire from capacitor and insulate.
8. Connect the blue wire of line cord to terminal C.
9. Install a rectifier element across TR and R to prevent loud bangs in the earpiece.

Dutch PTT T65
The circuit board build of this model phone does not allow for an easy conversion.  The details here will work, but if multiple bells are on the system then there may be difficulties. Try converting using 1 to 7 firstly.  If this works then just insulate the blue line cord wire.  If you have problems then follow all the instructions.

1. Remove original line cord.
2. Connect red wire of the line cord to terminal 1.
3. Connect white wire of the line cord to terminal 3.
4. Connect a 3.3k resistor to terminals 3 and 4.
5. Insulate the blue wire of the line cord.
6. Insulate the green wire of the line cord.
7. Test the phone and if it works OK - stop here.
8. If your phone has problems then carry follow the instructions 9 to 12.
9. Locate the capacitor - it is towards the front of the circuit board.
10. Looking from the front, cut the lead on the right hand side of the capacitor, in the middle.  Leave enough to reconnect if necessary.
11. Bend the piece of lead that is connected to the capacitor out of the way.
12. Solder the blue wire of the line cord to the wire that is still in the circuit board.
     

Ericsson (UK)
Any conversion will be found on the relevant page for the model. Click here for the UK Ericsson Telephone list.
If the model has no conversion information then please send a good quality picture of the circuit diagram pasted on the inside of the phone.
Both the circuit diagram number and telephone part number are prefixed with the letter "N".  The numbers bare no resemblance to each other.

Ericsson Dialog (table or wall) (Click here for diagram)
The circuit board build of this model phone does not allow for a complete conversion.  The details here will work, but if multiple bells are on the system then there may be difficulties. If you have problems with bells then leave out the resistor in which case the bell on this phone will not ring.

1. Remove original line cord.
2. Remove any link found between terminals 3 and 4.
3. Connect a 3.3k resistor to terminals 3 and 4.
4. Connect red wire of the line cord to terminal 2.
5. Connect white wire of the line cord to terminal 3.
6. Insulate the blue and green wires of the line cord.

Ericsson Type 1951 (Click here for diagram 31343)

1. Remove original line cord.
2. Connect red wire of the line cord to terminal 9.
3. Remove any link found between terminals 10 and 11.
4. Insert 3.3k resistor between terminals 10 and 11.
5. Connect white wire of line cord to terminal 10.
6. Remove the blue wire from capacitor C1 (grey oblong object).
7. Connect blue wire of the line cord to the blue wire which was removed above and insulate.
8. Insulate the green wire of the line cord.

This conversion is for both the Type 1951 wall and desk models

Ericsson DBH 160 1616 (Click here for diagram 361677)

1. Remove original line cord.
2. Connect red wire of the line cord to terminal 10.
3. Remove the link between terminals 6 and 8.
4. Insert 3.3k resistor between terminals 6 and 8.
5. Connect white wire of the line cord to terminal 8.
6. Remove the yellow wire from the capacitor C1 terminal.
7. Connect blue wire of the line cord to the yellow wire which was removed in 6. and insulate the joint.
8. Insulate the green wire of the line cord.

Ericsson DBJ 510 527 (Click here for diagram 361177)

1. Note colours of original line cord and then remove original line cord.
2. Connect red wire of the new line cord to the terminal where the old yellow line cord wire was terminated.
3. Connect white wire of the new line cord to the terminal where the old black line cord wire was terminated.
4. Insert a 3.3k resistor between the terminals where the old black and red line cord wires were terminated.
5. Remove the single wire connected to capacitor C1.
6. Connect blue wire of the new line cord to the terminal next to the red of the line is terminated..
7. Insulate the green wire of the line cord.

Ericsson DBN 1555 58 (Click here for diagram 429270)

1. Remove original line cord.
2. Red wire of the line cord to terminal 10.
3. Remove the link between terminals 6 and 8.
4. Insert 3.3k resistor between terminals 6 and 8.
5. White wire of the line cord to terminal 8.
6. Remove the yellow wire from the capacitor C1 terminal.
7. Connect blue wire of the line cord to the yellow wire which was removed above and insulate.
8. Insulate the green wire of the line cord.

Ericsson DE 200 (Click here for diagram 127478C)

1. Remove original line cord.
2. Connect red wire of the line cord to terminal 1.
3. Remove the link between terminals 3 and 5.
4. Insert 3.3k resistor between terminals 3 and 5.
5. Connect white wire of the line cord to terminal 3.
6. There is a wire that runs from the capacitor to terminal 6 on the induction coil.  Locate this wire and then remove the wire from the capacitor.
7. Connect blue of the line cord to the wire you have just removed and insulate.
8. Insulate the green wire of the line cord.
9. Connect a rectifier element to terminals 2 and 4.

Ericsson Ericofon (Cobra) (Click here for diagram Tfg3-39.247)
This conversion is for the variant with the circuit diagram Tfg3-39.247.  The circuit is shown to the right for identification and is probably a European (German) model. 

This phone is not quite right for a proper conversion, but can be converted to work but may or may not cause bell tinkle.

1. Remove original line cord.
2. Looking at the terminals and numbering from left to right.
3. Connect red wire of the line cord to terminal 2.
4. Connect white wire of the line cord to terminal 3.
5. Link terminals 1 and 2 together.
6. Insulate the green and blue wires of the line cord.

The above conversion requires verification from a convertor.

On UK lines this phone has been known to stop OAP link alarm systems from working, probably due to the 0.6uf capacitor.
 

French PTT Press Button (Click here for diagram M2193 issue 5)

1. Remove original line cord.
2. Connect red wire of the line cord to terminal L1.
3. Connect white wire of the line cord to terminal L2.
4. Connect blue wire of the line cord to terminal S.
5. Take one wire off the bell ringer and connect  to one wire of a 3.3k resistor.
6. Connect the other wire of the resistor to the bell terminal the wire was removed from.
7. Insulate the green wire of the line cord.
    

French PTT Model 24 (Mother-in-law phone)

1. Remove original line cord.
2. Connect red wire of the line cord to L1.
3. Connect white wire of the line cord to L2.
4. Connect blue wire of the line cord to S.
5. Take one wire off the bell ringer and connect  to one wire of a 3.3k resistor.
6. Connect the other wire of the resistor to the bell terminal the wire was removed from.
7. Insulate the green wire of the line cord.
    

French PTT Table Model U43 (Circuit diagram)

1. These instructions are for Diagram C10566.
2. Remove original line cord.
3. Connect red wire of the new line cord to terminal 9.
4. Connect white wire of the new line cord to terminal 10.
5. Connect blue wire of the new line cord to terminal 11.
6. The phone has no ringer in it, so a resistor does not have to be fitted.
7. Fit a Rectifier Element No. 205 across terminals 3 and 4.
8. Insulate the green wire of the line cord.

French PTT Wall Model U43 (Circuit diagram)

1. Remove original line cord.
2. Link terminals 11 and 12.
3. Link terminals 2 and 8.
4. Link terminals 10 and 18.
5. Connect red wire of the new line cord to terminal 15.
6. Connect white wire of the new line cord to terminal 14.
7. Connect blue wire of the new line cord to no where.
8. The phone has no ringer in it, so a resistor does not have to be fitted.
9. Fit a Rectifier Element No. 205 across terminals 5 and 6.
10. Insulate the green wire of the new line cord.

French PTT S63 (Socotel) (click here for diagram)
The terminal strips number from right to left.  The top terminals are even numbers and the terminals nearest the edge of the circuit board are odd numbers.  This conversion is the same for dial or press button.

1. Remove the original line cord.
2. Remove the metal link between  terminals T11 and T17
3. Connect a 3.3k resistor between T11 and T17.
4. Red wire of the new line cord to terminal T13.
5. White wire of the new line cord to terminal T11.
6. Blue wire of the new line cord to terminal T15.
7. Insulate the green wire of the new line cord.
8. Try the configuration above and if the bells do not work correctly then cut one of the leads of the 760 ohm resistor.  As the resistor forms part of the anti spark quench circuit then it should really be left in situ.

GEC Telephones
Any conversion will be found on the relevant page for the model. Click here for the GEC Telephone list.
If the model has no conversion information then please send a good quality picture of the circuit diagram which should be pasted on the inside of the phone.

Heemaf Type 1931 and 1952 (Circuit diagram)
This phone was made under licence from Siemens and Halske

The circuit diagrams are very similar in both models, so the instructions should cover both models.

1. Remove original line cord.
2. Locate the capacitor.  It has two terminals.
3. On one terminal there is a single wire - disconnect it from the terminal.
4. On the other terminal there are two blue/white wires.  Connect the blue wire of the new line cord to this terminal.  You need to either solder this spade connection or use thin wire and wrap the spade of the cord to the terminal.
5. Red wire of the new line cord to terminal A.
6. White wire of new line cord to terminal B.
7. Insulate the green wire of the new line cord.
8. The phone should work, but if the ringing is not right then insert a 3.3k resistor by removing one wire from the bell coils and then soldering the resistor to that terminal and the other end to the removed wire.

Heemaf Type 1954 (Htf 2214 BPZ) (Circuit Diagram) and 1955 (Htf 2129 BPZ4) (Circuit Diagram)

1. Remove original line cord.
2. Red wire of the new line cord to terminal 11
3. Remove the link between terminals 9 and 10.
4. Insert 3.3k resistor between terminals 9 and 10.
5. White wire of the new line cord to terminal 10.
6. Remove the blue wire from the capacitor.
7. On the 1955 table set terminate the blue wire from 5 above, on terminal 8 (the wire should just be long enough).
8. On the 1954 wall set connect a piece of wire to the blue wire removed from the capacitor (see 5 above) and then run this wire to the terminal strip terminating on terminal 8.
9. Connect blue of the new line cord to terminal 8.
10. Insulate the green wire of the new line cord.

ITT K500
(Circuit Diagram)

1. Remove original line cord.
2. Remove the yellow tube wire from terminal L2.
3. Remove the black tube wire from terminal K.
4. Remove the red tube wire from terminal G.
5. Remove the tube or just insulate the three unused wires above.
6. Connect the red wire of the line cord to terminal L1.
7. Connect the white wire of the line cord to terminal L2.
8. Link terminals A and K.
9. Blue wire of the line cord to terminal G.
10. Remove the red bell wire from terminal G and connect to one side of a 3.3k resistor.
11. Connect the other side of the 3.3k resistor to L2.
12. Insulate the green wire of the line cord.

There is no need to fit a Rectifier Element.

Kristian Kirk Telefonfabrikker F61 - 213251 (Circuit diagram)
This phone was made for the Jydsk (Jutland) Telephone Authority (Denmark)

1. Remove original line cord.
2. Ensure terminals L2 and KL2 are linked together.
3. Red wire of the new line cord to terminal L1.
4. White wire of the new line cord to terminal L2.
5. Blue wire of the the line cord to terminal J.
6. Insulate the green wire of the line cord.
7. Connect a Rectifier Element No. 205 across Terminals T and MT.

KTAS D30 (Click here for the Circuit Diagram)
The conversion differs on these two D30 models.

Conversion 1 - for model shown to right

1. Remove the link between terminals A and B and insert a 3.3K resistor.
2. Link terminals A and L1.
3. Remove link between terminals L2 and C.
4. Link terminals C and J.
5. Red wire of the line cord to terminal L2.
6. White wire of the line cord to terminal L1.
7. Blue wire of the line cord to terminal C.
8. Insulate the green wire of the line cord as it unused.

Conversion 2 - for model shown to right

1. Remove the link between terminals A and B and insert a 3.3K resistor.
2. Remove link between terminals L2 and C.
3. Red wire of the new line cord to terminal L2.
4. White wire of the new line cord to terminal L1.
5. Blue wire of the new line cord to terminal C.
6. Insulate the green wire of the new line cord as it unused.

Nordfern (RFT) W63a (Click here for diagram)
Due to the circuit of this phone being very basic, it will be best to convert in a manner that does not need much modification to the original.  The instruction are therefore simple, but bell tinkle may occur if other dial phones are used on the same line.

1. Remove original line cord.
2. Red of the new line cord to terminal 4.
3. White of the new line cord to terminal 2.
4. Insulate the green and blue wires of the new line cord as they are not used.
5. Do not fit a rectifier element as one is fitted already.

Northern Electric / NT 500 & 554
This model has 4 wires on the bell ringer
(Click here for wiring diagram)

1. Remove original line cord.
2. Connect the Red wire of the new line cord to L1.
3. Connect the White wire of the new line cord to L2.
4. Connect the Blue wire of line the new cord to G.
5. Remove the red/slate bell wire from terminal A.
6. Remove the red bell wire from terminal K.
7. Join the red/grey and red wires together and insulate.
8. Insulate the green wire of the new line cord.

Northern Electric / NT 500 & 554
This model has 2 wires on the bell ringer (100 DMK and 101 DMK)
(Click here for wiring diagram)

1. Remove original line cord.
2. Connect the Red wire of the new line cord to terminal L1.
3. Connect the White wire of the new line cord to terminal L2.
4. Connect the Blue wire of line the new cord to terminal G.
5. Locate the red wire from the bell and it should go to a connector on the main circuit board called A.
6. Remove the wire from terminal A by pulling it upwards.
7. The wire is spade ended and can now be connected on terminal L2.
8. Insulate the green wire of the new line cord.

Siemens W36, W38 and W48
For the W36 conversion click here
For the W38 conversion click here
For the W48 conversion click here
 

Siemens Halske S30054-S5137-B4-2
(Click here for diagram FG 54/5137)

1. Remove original line cord.
2. Red wire of the line cord to terminal 6.
3. White wire of the line cord to terminal 14.
4. Remove one wire from Capacitor C1 and insulate.
5. Move the Bell green wire from terminal 6 to terminal 5.
6. Insert a 3.3k resistor between terminals 5 and 6.
7. Blue of the line cord to Terminal 12.
8. Green wire of the line cord to terminal 13.
9. Do not fit a rectifier element as one is fitted already.

Swiss PTT - Tischstation Model PTT 1950 (Gfeller / Zellweger / Autophon)
(Click here for diagram Tf3 - 39.205)

1. Remove original line cord.
2. Red wire of new line cord to Terminal a.
3. White wire of new line cord to Terminal b.
4. Remove the green/white wire from the capacitor and connect this wire to the blue of the new line cord.
5. Cover the connection with insulation tape.
6. Locate terminals W1 and W2 and remove the metal link.
7. Connect a 3.3k resistor between terminal W1 and terminal W2.
8. Insulate the green wire of the new line cord.
9. If required, install a Rectifier Element No. 205 between Terminals T1 and T2.

Swiss PTT - Wandstation Mod PTT 1950 (Weidmann)
(Click here for diagram Tf3 - 39.211a)

1. Red wire of new line cord to Terminal a.
2. White wire of new line cord to Terminal b.
3. Remove the green/white wire from the capacitor and connect this wire to the blue of the new line cord.
4. Cover the connection with insulation tape.
5. Locate terminals W1 and W2 and remove the metal link.
6. Connect a 3.3k resistor between terminal W1 and terminal W2.
7. Insulate the green wire of the new line cord.
8. If required, install a Rectifier Element No. 205 between Terminals T1 and T2.
    

TN (Telefonbau Normalzeit) - S1a-112

This is basic conversion and does not involve manipulation of the internal wiring.  Other phones may tinkle when this telephone dials out.
This model may or may not have a button on top of the case, in front of the handset.

(Click here for diagram M18-112/16)
 

1. Red wire of new line cord to Terminal a.
2. White wire of new line cord to Terminal b.
3. Insulate the green wire of the new line cord.
4. If required, install a Rectifier Element No. 205 between Terminals F and F.

These telephones were made in West Germany and can be found all over Europe and Australia.  They are used on internal telephone systems (PAX) in the UK.

Why were they used - because they were a good price.
 

Western Electric 302A (No dial)  and 302B (Dial)
(Click here for WE 302A circuit diagram, click here for WE 302B circuit diagram, click here for the WE 302B schematic diagram)

To remove the case, slacken the two screws at either end of the base.  Do not touch the screw close to the side of the base.  Plastic cased (Tenite) telephones may smell strongly of cheese.  If this is the case then wash the cover inside and out in soapy warm water and remove any white residue, ensure the handle insert is also cleaned.  Leave in the sun for a few days and the smell will be much reduced.  If you are refurbishing American phones in the UK, ensure that you do not loose any screws as they use American threads which are very difficult to obtain in the UK.

1. Remove original line cord.
2. Red wire of new line cord to terminal L1.
3. White wire of new line cord to terminal L2.
4. To the middle right of the base there is a small square Paxolin board with two terminals.  Under one of the terminals will be two wires.
5. Remove both wires and connect a 3.3k resistor between the two terminals.
6. The two wires previously removed must now be connected, one to each terminal.
7. Insulate the Green wire of the new line cord.
8. Insulate the Blue wire of the new line cord.
9. Remove the earpiece and the receiver insert.
10. Two springs will be seen - slacken the screws on the springs.
11. Insert the wires of a Rectifier Element No. 205 under each of the springs and tighten the screws.
12. Replace the receiver insert and earpiece cover.

Dial wiring information

Western Electric 500 - With Network 4293 (Click here for the circuit diagram)
This model will most probably have a computer style connector on the line cord.  It would be better to use a new BT style plug needed cord.

1. Remove original line cord.
2. Red wire of line cord to terminal L1.
3. White wire of line cord to terminal L2.
4. Insulate the Blue wire of line cord.
5. Insulate the green wire of the line cord.
6. Remove the red wire between terminals A and L2
7. Connect a 3.3k resistor between terminals A and L2.

Western Electric 500C & 500D - With 425B Network (Click here for the circuit diagram)

1. Remove original line cord.
2. Red wire of line cord to terminal L1.
3. White wire of line cord to terminal L2.
4. Blue wire of line cord to terminal G.
5. Remove the red/slate bell wire on terminal A and connect to one side of a 3.3k resistor.
6. Connect the other side of the resistor to terminal K.
7. Insulate the green wire of the line cord.

Western Electric 502 & 510F (May give bell tinkle on outgoing dialling)

1. Remove original line cord.
2. Red wire of line cord to terminal L1.
3. White wire of line cord to terminal L2.
4. Blue wire of line cord to terminal RW (on the terminal strip).
5. Connect a piece of wire between terminal L2 (on the Network Card) and terminal W (on the terminal strip).
6. Remove the wires on terminal A and terminal K (on the Network Card) and connect them to a 3.3k resistor.
7. Insulate the green wire of the line cord.

Western Electric 2500 (Click here for circuit diagram) - For WE 2500DM
These are MF telephones that were supplied in different variants.  They generally have an RJ10 socket in the casing for a line cord, so buy a UK plug ended cord.  The bells are not wired as standard and therefore may not operate correctly.

Note - Sometimes they will not dial out, try swapping the red and green wires on terminals L1 and L2.

To wire a cord with spade terminals follow the instructions below.

1. Red wire of new line cord to terminal L1.
2. White wire of line cord to terminal L2.

Onyx Telephones

Italian made telephones produced from the late 1970's, mostly from a company called Telart in Italy.  The cases are made from flat pieces of marble, with mitred corners, glued together.  The base is metal and has a circuit board fixed to it.

These have an oblong circuit board inside.  There are three distinct circuit boards.  To identify which type you have, the base plate must be removed.  The early versions have screw terminals and you will have to locate the handset cord and see how many terminals it is connected to.  It will be three or four terminals.

The three terminal type will be labelled R, M and MR (see picture below).  The four terminal type will be labelled R, R, M and M probably with a link between the M and a R terminal, which is closest to terminal S2.

The third type is a modern version which supports the press button dial unit.  It just has push fit connectors. 

These circuit boards are not of best quality and one should always check for breaks in the tracks on the rear of the board.  They can be repaired by scrapping back the varnish around the crack and bridging the crack with solder or by soldering a small piece of wire across the crack.

Three terminal model

1. Remove the existing line cord.
2. Remove any link between b and S terminals.
3. Red wire of new line cord to terminal a.
4. Connect a 3.3k resistor between terminal b and terminal S.
5. White wire of new line cord to terminal b.
6. There are two terminals S and S1 next to each other.  Blue wire of the new line cord connects to S.
7. Insulate the green of the new line cord as it is not used.
8. Cut through one of the leads of the 1uf capacitor and ensure that they do not make contact.
9. If there are loud clicks in the earpiece, connect a Rectifier Element No. 205 between the R and MR terminals.

Four terminal model

1. Remove the existing line cord.
2. Remove any link between terminals b and S2.
3. Red wire of new line cord to terminal a.
4. Connect a 3.3k resistor between terminals S2 and b.
5. Link terminal B to terminal S2.
6. White wire of new line cord to terminal b.
7. Insulate the green and blue wires of the new line cord as it is not used.
8. Connect a Rectifier Element No. 205 across terminals R and R.

Push fit model
As the wires have special push fit connectors there is a choice of how to connect the line cord.  Either keep the original line cord and fit a junction box at the end and the connect the new line cord to it.  Or cut the line cord off at the phone end leaving about 4 inches of wire.  The new line cord could be connected with push type connectors.

1. See above for information on how to connect the new line cord..
2. Only connect the red and white wires of the new line cord to the red and white wires of the original cord..
3. Cut the wire link between the terminals S1.
4. Bend the two wires upwards and then solder a 3.3k resistor between them.
5. Another option would be to remove the wire link between terminals S1 with a soldering iron and just replace it with the resister - your choice.

Telart circuit boards and circuit diagrams

This is the 3 terminal type and they are on the left hand side of the picture
The long yellow component to the right is the 1uf capacitor
The picture above shows the original wiring before conversion
Circuit digram

Push fit connector type circuit board with press button dial pad
Picture shows unconverted telephone

Circuit diagram for push fit connector type circuit board
Note that the bell is connected to the terminals 'S' and that terminals 'S1' are linked together.

This circuit diagram is from the tall wooden gilded telephone with the handset on top
The layout of the circuit board is shown schematically

Last revised: April 09, 2024