TELEPHONE No. 745 & 8745


TELECOMMUNICATIONS INSTRUCTION
C MARKETING INSTALLATION
3 Internal
B1030
Issue 1, April 1973

TELEPHONE No. 745 (WEATHERPHONE)
Description


GENERAL
The Telephone No. 745 is a weatherproof telephone for use on DEL's and PBX extensions in Auto and CB areas on lines up to 1000 ohms.  The circuit details are shown in diagram N845.

Click diagram - N845.


COMPONENTS AND CIRCUIT
The transmission circuit is the same as that used on the Telephone No. 746 but a different printed board is used and two of the components have additional protection against the ingress of moisture.  The telephone is protected by neoprene rubber seals between the backplate and body and the body and door.  Access to the printed circuit board is gained by opening the door and undoing the two screws, at the top and bottom of the instrument body.  When it is required to reassemble the backplate to the instrument body, these screws must be fully withdrawn otherwise they will foul their locating pillars.

A micro switch mounted on the backplate forms the gravity switch.  When the handset is correctly clipped into the body, the earpiece depresses a plunger fitted to the body which operates the gravity switch.  A screw fitted to the gravity switch mounting bracket provides a lineman's latch.  This latch is not self restoring and care should be taken to slacken the screw before reassembling the telephone.  After slackening the lineman's latch screw to release the gravity switch the locknut must be tightened to ensure that the screw does not work loose (e.g. due to vibration).  Ensure that tightening the locknut does not advance the screw thereby jamming the action of the gravity switch.

The bell mechanism is similar to the Bell No. 59 except, to provide weather proofing, the armature is fixed to a separate pivot pin which passes through a long bearing fixed through the backplate.

Fitted to the backplate are two twin terminal blocks that are suitable for all sizes of cable up-to 40 lb. conductors.

The dial fitted to the body is a Dial Automatic No. 21 FA Steel.  For CB use the dial may be replaced by a Dial Automatic Dummy No. 3A Black.

An additional gravity switch (Switch No. 20D), used for C wire signalling etc may be fitted, and to provide PBX recall facilities a Switch No. 27A-1 should be fitted, as shown in Diagram N 845.  Switch No. 26A-1 may be used to provide the bell on-off facility.

FITTING INSTRUCTIONS
The telephone may be fitted to a wall or flat fixture or alternatively may be mounted on a post or pole.  For fixing use 3 Screws for Wood No. 12 Csk Hd at least 2in long or 2BA Csk Hd screws depending on the type of fixture.
For pole or post mounting, the following items are available:-

POLE DIAMETER ITEM DESCRIPTION ITEM CODE No
3-6 inBracket, Telephone 17A 434700
6-9 inBracket, Telephone 17A 434701
9-12 inBracket, Telephone 17A 434702

The lead-in to the telephone should be enclosed in Conduit No. 2. Secure the conduit to the telephone with locknuts.  To prevent the entry of moisture, the end of the conduit remote from the telephone, if external, should be made to point in a downwards direction.  This end should also be fitted with a Bushes Conduit Smooth Bore F to prevent abrasion of the cable.  If it is considered suitable a cable gland may be fitted to the telephone conduit bush and the conduit omitted.

To fit a Switch No. 20D alongside the existing gravity-switch:-

(i) Remove the four screws securing the gravity switch bracket to the baseplate.
(ii) Remove the screw securing the micro-switch to the bracket.
(iii) Place the Switch No. 20D alongside the existing gravity switch micro-switch so that the peg in one locates with the hole in the other.
(iv) Locate the two switches between the side limbs of the gravity switch bracket and secure with the screw provided with the Switch No. 20D.
(v) Screw the gravity switch bracket back onto the backplate.
(vi) Route the connection leads to the left of the bell mechanism to prevent fouling the bell armature and terminate in accordance with the circuit diagram.

When it is required to have the door locked, replace the dummy lock by a Lock No. 43A, transpose the lock plate stored on the right-hand side of the backplate and the two sealing screws fitted to the interior of the body cavity.

BELL-GONG ADJUSTMENTS
To adjust the bell gongs, loosen the two bell clamping screws that protrude through holes in the printed board, rotate the gongs to obtain the required adjustment and retighten the clamping screws.

To obtain this adjustment it is not necessary to dismount the telephone.  The gongs can be rotated by applying pressure to the edge of the gongs with a finger and the armature moved smartly from poleface to poleface to ensure that a clear ring is obtained from each gong.

GRAVITY SWITCH ADJUSTMENT
The gravity switch itself should not require adjustment.  If incorrect operation of the gravity switch does occur check that the body of the telephone is seating correctly on the backplate before opening the telephone and that the plunger is free in the body. T he screws securing the case to the backplate should be fully tightened as this will affect the operation.  Due to misuse the receiver hook may be distorted and cause non-operation of the gravity switch.  This is usually evident by the fact that the handset will not securely clip into position.  This condition can be corrected by removing the hook and bending with a pair of pliers until satisfactory operation of the gravity switch can be obtained.

PARTS
The following items are available:-

Handset No. 3 Black
Cord Inst No. 4/113AX 6 in (Cord for Handset No. 3)
Switch No. 20D
Switch No. 26A-1
Switch No. 27A-1

When it is required to have the door locked, a Lock No. 43A (Item code number 434584) is available.

Telephone No. 8745 was fitted with high impedance bell coils and a new style Plug and Socket cord.

Circuit diagram - N845.

Telephone No. 745P was introduced and could be fitted with press button units for LD or MF signalling.  This variant was later renamed the Telephone No. 6744 (MF) and the Telephone No. 6745 (LD)

How to wire your Telephone No. 745 to make it work on Plug and Socket

Made by Ericsson - Model N1248A1



WORKS SPECIFICATION S(W) 2136
FOR
TELEPHONE 745 (weatherproof)

1. GENERAL
The Telephone 745 is a weatherproof telephone for use on D.E.L.s and. P.B.X. extensions in Auto and C.B. areas on lines up to 10OO) No provision is made for its use on shared service connections.

2, CONSTRUCTION
The telephone consists of three parts, namely door, body and. backplate.  The first two are of die cast aluminium and the backplate of heavy gauge aluminium alloy sheet.  The door is hinged to the body and is slightly larger than the body to enable the door to be opened without the need for a handle.  A toggle spring fitted between the body and the door holds the door either in the fully open or closed position.

Mounted on the backplate is a printed board which carries the telephone components. Three stand-off legs are fitted to the backplate through which are passed the fLxin6 screws. External 4. in. diameter bell gongs are fitted to the rear of the backplate within the space provided, by the stand-off legs.
The body is hinged to the backplate on the left hand side and is looked to the backplate by two screws located at the top and bottom of the body cavity.

The Handset is retained in the body cavity by a hook under the receiver cxid a spring clip above the transmitter.  The door has been so arranged that when it is closed it ensures that the handset is correctly clipped in position.

Two bushes threaded for Conduit No. 2, one fitted with a blanking plug, are fitted to the bottom of the backplate to provide cable entry.

The joints between the backplate and body and the body and door have neoprene rubber seals to prevent the entry of water.
Provision is made for a lock to be fitted to the door should this be required.  The telephone when issued is fitted with a dummy look to seal the opening in the door.

3. COMPONENTS AND CIRCUIT
The transmission circuit is the same as that used on the Telephone 746 but a different printed board is used and two of the components have additional protection against the ingress of moisture.

A micro switch mounted on the backplate forms the gravity switch. When the handset is correctly clipped into the body, the earpiece depresses a plunger fitted to the body which operates the gravity switch.  A screw fitted to the gravity switch mounting bracket provides a linesmans latch. This latch is not self restoring and care should be taken to slacken the screw before reassembling the telephone.

The bell mechanism is similar to the Bell No. 59 except, to provide weatherproofing, the armature is fixed to a separate pivot pin which passes through a long bearing fixed through the backplate.

Fitted to the backplate are two twin terminal blocks that are suitable for all sizes of cable up to 40 lb conductors.

The dial fitted to the body is a Dial Automatic No. 21 LA Blue which is not a stocked item. For C.B. use the dial may be replaced by a Dial Automatic Dummy No. 3 Black.

An additional gravity switch may be fitted and to provide PBX recall facilities the handset may be replaced by a Handset No. 6 Black.
Pending issue of N 8if5 the circuit diagram is given in the appendices to this Works Specification.

4. FITTING INSTRUCTIONS
The telephone may be fitted to a wall or flat fixture or alternatively may be mounted on a post or pole. For fixing use 3 Screws for Wood No. 12 Csk.Hd. at least 2.75in long or 2BA CSk.Hd. screws depending on the type of fixture.

For pole or post mounting pole clamps in three sizes as follows are available on local purchase from:-
Plessey Telecommunications Group
Ericsson Telephones Ltd.
Beeston
Nottingham
NG-9 I LA

Pole diameter Catalogue No. Approximate price
3 - 6 in. N 111333A 2.8.9
6 - 9 in. N 111333B 2.17.0
9 - 12 in. N 111333C 3.5.3


The lead-in to the telephone should normally be enclosed in Conduit No. 2. Secure the conduit to the telephone with locknuts.  To prevent the entry of moisture, the end of the conduit remote from the telephone, if external,, should be made to point in a downwards direction.  This end should also be fitted with a Bushes Conduit Smooth Bore 0.75in. to prevent abrasion of the cable.  If it is considered suitable a 0.75in. cable gland may be fitted to the telephone conduit bush and conduit omitted.

To provide PBX recall fit a Handset No. 6 Black and Cord Inst. No. 6/55Ax Grey 6 in. in place of the Handset No. 3 Blue and. Cord Inst. No. 4/113AX Blue 6 in.  The recovered handset and cord should be returned to stock.

To provide extensions with C wire signalling provide a Handset No. 6 and cord as previous paragraph and also fit a Switch No. 20D to the gravity bracket as follows:-
(i) Remove the four screws securing the gravity switch bracket to the baseplate.
(ii) Remove the screw securing the micro-switch to the bracket.
(iii) Place the Switch No. 20D alongside the existing gravity switch nro-switch so that the peg in one locates with the hole in the other.
(iv) Locate the two switches between the side limbs of the gravity switch bracket and secure with the screw provided, with the Switch No. 20D.
(v) Screw the gravity switch bracket back onto the backplate.
(vi) Route the connexion leads to the left of the bell mechanism to prevent fouling the bell armature and terminate in accordance with the circuit diagram.

Prior to the Switch No. 20D being available from Purchasing and Supply Dept., stocks of this item are available from T.H.Q. TDI .1.1, REG.23, PROCTER HOUSE, 100 HIGH HOLBORN, LONDON, W.C.2.

When it is required to have the door locked, obtain on local purchase a Lock, Catalogue No. S104L, from Yale Locks and Hardware, 207 The Vale, Acton, London Vi-3., price approximately 18/9d. each, replace the dummy lock by the lock, transpose the lockplate stored on the right-hand, side of the backplate and the two sealing screws fitted to the interior of the body cavity.

5 MAINTENANCE INSTRUCTIONS
5.1 To adjust the bell armature travel loosen the two screws clamping the magnet and slide the yoke extension clear of the armature. Loosen the two screws fixing the bell coil assembly to the backplate, move the bell coil assembly to obtain an armature travel of 20-25 mil., 10-12 mil if 50 Hz operation is required, then tighten the bell coil assembly fixing screws. Slide the yoke extension towards the armature to obtain just perceptible clearance between the armature and the yoke extension, check that the armature does not contact the yoke extension when the armature is moved from pole-face to pole-face, tighten the two clamp screws and recheck that the required travel and clearance have been obtained.

5.2 To adjust the bell gongs, loosen the two bell clamping screws that protrude through holes in the printed board, rotate the gongs to obtain the required adjustment and retighten the clamping screws.

To obtain this adjustment it is not necessary to dismount the telephone. The gongs can be rotated by applying pressure to the edge of the gongs with a finger and the armature moved smartly from pole-face to pole-face to ensure that a clear ring is obtained from each gong.

5.3 The gravity switch should not require adjustment. If incorrect operation of the gravity switch does occur check that the body of the telephone is seating correctly on the backplate and that the plunger is free in the body.  Due to misuse the receiver hook may be distorted and cause non-operation of the gravity switch.  This is usually evident by the fact that the han1set will not securely clip into position.  This condition can be corrected by applying pressure to the uppermost part of the hook until satisfactory operation of the gravity switch can be obtained.

5.4 The dial fitted to the telephone is not a stocked item.  Prior to the full introduction of All Figure Numbering if a dial requires changing, replace it by a Dial Automatic No. 21 LA Black, transferring the blue finger plate from the old to the new dial.  Alternatively, if available, a Dial Automatic No. 12 LA may be used.

After the full introduction of A.F.N. use a Dial Automatic No. 21 FL clear for maintenance replacement.

5.5 The following items are available for maintenance replacement:-
Handset No. 3 Blue
Handset No 6 Black (As in paragraph 1)
Cord. Inst. No. 4/113AX Blue 6 in.
Cord. Inst. No. 6/55AX Grey 6 in.
Dial as in paragraph 5.4
Switch No. 20D
Lock
Pole Clamps

If other replacement parts are required the complete telephone should be changed.

Dated 1968


Additional information

ModelMarkGreyIntroducedRemarks
Tele 745Mk 1y5/68 
Tele 745MMk 1y12/77Metric conduit entry
Tele 745PMk 1y11/83Push button version
    11/83PBU 80A - for Loop Disconnect
    11/83PBU 81A - MF4

 


 
Additional Pictures
Front View
Note the dummy Lock
 
View with door open
 
Rear View

 

 

 
 
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Last revised: January 18, 2020

FM