TELEPHONE No. 776
Installation & Maintenance Guide


Installation

The fitting work required in connection with this telephone centres mainly upon the siting and fixing of the Bell Unit. The following guide notes concerning its installation should be read thoroughly before any cabling work is undertaken; including the entry of dropwiring to the building.

Two methods of installation are shown in Figs 1 & 2.

FITTING BELL UNIT SA 4271
The bell unit is made up of three parts, Cover, Base Unit and Mounting Plate.

PREPARATION FOR FIXING
Remove the cover by inserting the blade of a small screwdriver through the sound hole (see Fig. 3 above), gently press against the sprung lug, then lift off the cover.

With the cover removed the mounting plate can be slid out of the base unit, ready for fixing into position.

POSITIONING THE MOUNTING PLATE
The mounting plate can be fixed to a flat surface in any one of 3 positions.

The correct position will depend upon:-
1. The entry point of the internal cable or drop wire
2. Whether the bell unit is to be mounted Horizontally or Vertically. (See Fig. 4 below).

THE BASE UNIT AND COVER MUST NEVER BE FIXED DIRECTLY ONTO A SURFACE WITHOUT THE MOUNTING PLATE.


FIXING THE MOUNTING PLATE
The mounting plate should be fixed into position using the slots in its bad plate. The use of slots instead of holes enables the mounting plate to be accurately levelled before the fixing screws are finally tightened, 2BA or 48A bolts should be used for fixing to conduit outlets, and number 8 roundhead woodscrews for other types of surfaces.

An extension bracket, also an angled adaptor are available for fitting the bell unit above skirting boards and to wooden window frames without the need to resort to wall plugging. See Figures 5-8.

Before fixing into position ensure that there is a clearance of about 25mm (1") surrounding the mounting plate so that the base unit and cover can be fixed to it.

CABLING AND FITTING THE BELL UNIT BASE TO THE MOUNTING PLATE
Fig. 9 shows the cable entry points to the Mounting Plate and Bell Unit base. To serve as an example these guide notes on cabling refer to a Bell Unit being fitted horizontally.

SEQUENCE

  1. Run the cable to the appropriate entry point in the Mounting Plate.
  2. Feed the cable through the appropriate entry point in the base unit.
  3. Being careful not to trap the cable, engage the lugs on the back of the base unit into the slots on the sides of the mounting plate. To engage the lugs, the base unit should be positioned approx. 15mm (/8" in.) above the bottom of the mounting plate.
  4. Pressing the base unit backwards and downwards, slide it into position on the mounting plate.

TERMINATION
Dropwire should be terminated on the right hand compression type terminal block, and internal cables on the left hand one.
After termination, the cover can be replaced by pushing it over the base unit, until it snaps firmly into place. The Bell Unit is now anchored firmly to the mounting plate.

Wall Mounting The Telephone and Bell Unit Using a Brackets Telephone D93235
The Brackets Telephone is in 3 parts (Fig.10) and when fitted to the Mounting Plate issued with the Bell Unit, it will house the bell unit base and form a shelf upon which the telephone will stand. Figs 11-15 illustrate the steps and the order in which they should be undertaken, when fitting the bracket.

First, remove the cover from the Bell Unit and discard. then slide the mounting plate out of the base unit.

Fix the Mounting Plate firmly to a flat surface or conduit outlet, in a HORIZONTAL position and at the desired height (ask customer). A clearance of 125mm (5") will be required above the top edge of the plate so that the telephone can stand on the shelf. If fitting to a conduit outlet, feed the cable through the slot indicated.

Remove the shelf from the Brackets Telephone by pressing it upwards at the front edge.

Feeding internal cable through the right hand entry, or dropwire through the left, slide the bracket down onto the lugs of the Mounting Plate, being careful not to trap the cable. The bracket is 'fully home' when the bottom edge of both mounting plate and bracket are 'flush'.

Remove the cord anchor block fixing screw and slide the block out of Bell Unit base by pulling on the cord grommet. Re-position the cord grommet as illustrated, then replace the anchor block and fixing screw. Be careful not to trap the cord conductors when tightening the screw.

The cord should now be entering the underside of the Bell Unit's base.

Feed the Bell Unit upwards through the Brackets Telephone. With the bell gongs uppermost and towards you, engage the base of the Bell Unit under the lugs on the front edge of the bracket, then push it downwards at the back and it will snap into position.

Terminate the cable to the Bell Unit. Internal cables on the right hand terminal block, dropwire on the left.

Refit the shelf, by engaging the lugs into the slots in the bracket, push it down at the front and snap into position.
The bracket is now locked securely to the mounting plate.
To remove the bracket from the mounting plate, remove the shelf and slide the bracket upwards.

Exclusive Service Working
The telephone 2/SA 427 1-1 is supplied strapped and with cords terminated for Exclusive Service working. Installation consists of fitting the Bell Unit and terminating the line to it. Because a commemorative motif is to be fitted in the dial centre, the telephone number label will be fitted to the carrying handle under the handset, using a transparent plastic clip (Fig. 16).

Shared Service Working
The Telephone 2/SA 4271-1 is modified for shared service working by adding a Thermistor lA/1 to the Bell Unit and a Switch 30A-2 to the telephone. The switch should be fitted to the right hand front edge of the telephone (Fig. 17). Packed with the switch, is Dummy Switch (Part 1/DLE/85) which should be fitted to the left hand front edge, so as to give the telephone a balanced appearance.

Installing Switches
To fit the switches, remove the telephone cover by slackening the screw in the telephone base (Fig. 18). The cover is then lifted clear of the base in two operations, (1) using both hands, place the thumbs in the dial centre, with fingers holding sides of cover. (2) keeping thumbs in position pull cover towards you, and off. To replace, pass the slots in the cover over the receiver rests, and then hinge it forward over the dial. Finally, snap the front edge lugs into position, and tighten the retaining screw in the base.

 

Add-on Units
'CALL EXCHANGE' switches (Switch No. 30A-2)should be fitted to the right hand front edge of the telephones and 'Bell ON/OFF' (Switch No. 30B-2) switches should be fitted on the left, at extensions.

If only one additional switch is installed then a dummy switch (Part 1/DLE/85)is fitted on the opposite side.

A switch 19A-1 can be bolted to the side of the existing gravity switch as shown in Fig. 20.


 

For old style Plan 4 arrangements a Jack 136A can be fitted in the Bell Unit.

 


Maintenance

Replacement parts
Handset - Handset No. 15A
Handset Cord - Cord Inst 4/123AX Grey 200mm
Instrument Cord - Cord Inst 6/63AX Grey 700mm
Dial - Dial Auto 21 FA Clear
Transmitter - Transmitter Inset 16
Receiver - Receiver Inset 4T
Feet - Part 2/DBU/259
Call Exch/Recall Switch and Dummy - Switch 30A-2
Bell On/Off Switch and Dummy - Switch 30B-2

Complete Items
Telephone and Bell Unit - Telephone 2/SA 4271-1
Telephone - Telephone SA 4271
Bell Unit - Bell Unit SA4271
 

Dismantling and Re-assembling the Telephone 2/SA4271-1
COVER
To remove the telephone cover by slackening the screw in the telephone base (Fig. 18). The cover is then lifted clear of the base in two operations, (1) using both hands, place the thumbs in the dial centre, with fingers holding sides of cover. (2) keeping thumbs in position pull cover towards you, and off. To replace, pass the slots in the cover over the receiver rests, and then hinge it forward over the dial. Finally, snap the front edge lugs into position, and tighten the retaining screw in the base.

HANDSET 15A
The hand set is constructed from two separate mouldings held together by a screw at the receiver end.
Remove this screw and pull the handset apart, some force may be needed but do not prise apart with a screwdriver.
To remove the transmitter and receiver, push down on the black plastic spring clips and slide outwards, they are now free to take out, (see Fig. 24).

DIAL
The dial is removed by slackening the clamping screw (Fig. 25) and then gently pulling the dial forward. It is not necessary to completely remove the clamping screw.
When replacing the dial ensure that the finger stop is positioned between the locating ribs before tightening the clamping screw (Fig. 25).
Make sure that the special motif is replaced correctly.

Add On Units
SWITCHES (Cover removed)

To remove the switches and dummies, position a number 2 screwdriver between the projection on the rear of the switch and the sprung lug on the telephone base. Twist the screwdriver, and at the same time apply pressure to the switch lever in an operating direction (Fig 26). The switch then comes away from the body of the telephone.
NOTE: CARE MUST BE TAKEN WHILST CARRYING OUT THE ABOVE INSTRUCTIONS, OTHERWISE A HAND INJURY CAN OCCUR.

LINESMANS LATCH
This is pivoted on a pin on the right hand side of the cradle lever (when telephone viewed from the front). To engage, it should be pulled gently upwards until its movement is stopped. The cradle lever should now rest on the top of the micro-switch case, this will cause the gravity switch to be in the 'on hook' position, (see Fig 27).

The latch is self releasing when the telephone cover is replaced, or can be restored manually.


GPO Jubilee Year Telephone Guide Notes April 1977
 

 
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Last revised: February 09, 2020

FM