Circuit diagram N876.

How to wire a Telephone No. 776 or Jubilee telephone to make it work on Plug and Socket

More pictures of the Telephone No. 776

Jubilee version

Marketing Brochure - PH2431

3 Internal
Issue 1, Nov 1978

(Compact Telephone)

This Instruction describes the Telephone No. 776-1 which is a new style telephone, marketed as the "Compact Telephone".

The telephone instrument and bell unit are separate items (Telephone No. 776 and Bell Unit No. 776) but are issued from stock connected together by an extensible cord to form the Telephone No. 776-1. Exceptionally, with the addition of a suitable block terminal to terminate the telephone cord, the telephone and bell unit may be sited in different locations and interconnected by internal cable. The telephone is available in a choice of colours, light grey, brown or blue, whilst the bell set is in light grey only. The telephone can be converted to a wall type instrument by using a Bracket Telephone 18A, in the colour to match the telephone. The telephone and bell unit consist of a number of moulded parts secured mainly by snap action locking tabs. Screw fixing of parts and components is kept to a minimum.

The Telephone No. 776 is smaller than existing 700 type instruments enabling it to be fitted on shallower window ledges or shelves than is possible with other telephone apparatus. It has a carrying handle and an extensible cord that will extend to approximately 3 metres in length. There is provision for an add-on switch to provide 'call exchange and 'operator recall' conditions when required. An auxiliary gravity micro-switch may also be fitted.

The telephone cover is secured by two projections, formed on the front edge of the cover, engaging in angled slots formed in the base moulding immediately below and to either side of the dial, and a single retaining screw adjacent to the rear edge of the base. To remove the cover the captive retaining screw which is accessible from under the telephone must first be disengaged. The instrument cover should then be lifted upwards and forwards until it clears the bottom edge of the dial, the front of the cover can then be lifted upwards and rotated towards the rear, clear of the telephone base. To replace the cover present it to the telephone so that the dial aperture passes over the dial. The two projections on the cover will engage and locate with the angled slots in the base. Press the rear of the cover down onto the base and secure with the retaining screw.  (If the cover does not clear the dial finger plate - then remove the finger plate and replace later).

The Bell Unit No. 776 has suitable terminations for drop wire in addition to terminations for internal cable, thus avoiding the need for a separate terminal block. Dimensions are less than existing bellsets, permitting the unit to be mounted within the majority of window alcoves, etc. It is a slide-on fit to a wall plate which can be screw fixed to a flat surface, conduit box, or with the addition of angle brackets to skirting boards or wooden window sills. The snap fit cover locks the bell unit to the wall plate.

When used on Plan 4 installations it can be fitted with a jack into which can be plugged a portable telephone. It can be mounted within a wall bracket which also provides a secure shelf for the telephone. When mounted within the wall bracket the bell unit can also be provided with a jack.

The bell unit cover (Part 1/DCO/760) is a snap action fit to two sprung lugs formed on the bell unit base. The cover can be removed by inserting the tip of a small screw driver through the sound opening slots located at each end of the cover just sufficient to disengage the sprung lugs from the locking projections formed on the inside of the cover. The cover can then be lifted off the bell unit base.

The bell unit base (Part 1/DBA/217) provides a mounting for a Bell No. 79A, a 1.8 micro-farad capacitor and an instrument cord anchor block (Part l/DBL/124) which is replaced by a Jack No. 139A when used on a Plan 4 installation. It contains two groups of terminals. One has seven terminals on which are terminated either the cord conductors or the Jack 139A leads. Six of these terminals are permanently connected to the other group of six terminals. All of the second group of terminals are for terminating internal cable and three are also suitable for terminating drop wire.

The bell is fitted with a three position volume control, operated by a lever which projects from under the bell unit cover, or lower front edge of the bracket telephone. The control is effected by mechanically impeding the travel of the bell hammer rod. The volume control lever is also used to provide the bell cut off facility.

The telephone and bell unit can be used on exclusive or shared service lines either as:-

  • direct exchange line,
  • main or extension of a Plan 1A installation,
  • at a Plan 4 installation,
  • direct PBX extension, internal or external,
  • the compact telephone may be used with 700 type telephones on a Plan 1A, or a Plan 1A and Plan 4 combination. However, it is not permissible to use both compact and 700 type telephones as portable instruments on the same Plan 4 installation, as the plug and the jack wiring for each model is different.

The Bell Unit No. 776 must never be secured directly to a wall or other flat surface. To mount the bell unit it is first necessary to secure the ,mounting plate (Part 1/DPL/2270), which is included with each Telephone No. 776-1, or bell unit, to the surface upon which the bell unit is to be mounted. To release the mounting plate from the bell unit, the bell unit cover must be removed as described above. The preferred method of mounting the bell unit is with the bell gongs uppermost, but where there is limited space it may be fitted with the bell gongs facing either to the left or right. The bell unit MUST NOT be fitted with the bell gongs facing downwards.

The mounting plate has a variety of slots allowing various fixings; it may be by two Round Head screws secured to a conduit box (screws aligned horizontally or vertically), a wood backboard or fixture, or a hard wall surface by plugged screw fixing using three No. 8 roundhead wood screws.

By using an angle bracket (2/DBR/686 or 2/DBR/687) in conjunction with the mounting plate, the bell unit can be fitted to a skirting board, window frame or similar structure as described later.

One of the long edges of the mounting plate has two projections of only one thickness of metal. For the purpose of explanation this will be considered to be the bottom edge of the mounting plate. The bell unit has a slide fit to the mounting plate and is locked in position by the cover overlapping this edge of the mounting plate.

The fixing procedure is as follows:-

Remove the bell unit cover and release the mounting plate.

The mounting plate must be positioned, before fixing, so that there is a minimum gap of approximately 25mm (1 inch) between the top and side edges of the mounting plate and any adjacent wall, window frame, or other obstruction. This gap is necessary to permit the bell unit to be engaged with the mounting plate before it is slid into its final position, and also to provide clearance for the cover to be fitted.

Secure the mounting plate to the wall or flat surface with the previously described edge at the bottom. Any of the slots stamped in the mounting plate may be used for the screw fixing.

Fit the bell unit to the mounting plate. This can be achieved, where there is a minimum of 25 mm (1 inch) clearance above the mounting plate by locating the lug on each side of the rear of the bell unit with the spaces formed in the sides of the mounting plate and then sliding the bell unit home.

All cables are fed to the group of six terminals, with surface run cables leading up to the recessed corner of the bell unit. When the mounting plate is secured to a conduit box the cable may be passed through any of the unused slots in the mounting plate, except those formed by the two flanges, if a Bracket Telephone No. 18A is to be fitted.

All of the six terminals are suitable for terminating internal cables. Terminals B11, 12 and 13 are also suitable for direct termination of dropwire. The dropwire conductor should be fed straight into the clamp device after removal of the insulation and NOT wrapped around the screw terminal. If required both dropwire and internal cable conductors may be terminated on these three terminals, the internal conductor being conventionally wrapped round the screw above the clamping plate. The group of seven terminals are for cord termination only and should not be used to terminate cables.

Having run and terminated the cables make, sure that the bell unit is correctly aligned on the mounting plate, and then replace the bell unit cover.

Two brackets are available to permit the bell unit and its mounting plate to be provided in a variety of situations that would otherwise require wall plugging; each is supplied complete with two 4BA screws and washers. These brackets will accept the bell unit with either the gongs or the cord entry uppermost.

Part 2/DBR/686 is an angle bracket allowing the mounting plate to be secured at a right angle to a window sill, etc. Two holes for suitable wood screws are provided in its narrowest side for securing to the window sill. After securing, the Part 1/DPL/2270 (mounting plate) should be screwed to the widest side of the angle bracket with the two 4BA screws and washers. Any two of the three tapped holes may be used depending upon the position required for the bell unit.

Part 2/DBR/687 is an extension bracket which is secured to a skirting board but has a fixing for the mounting plate that positions the bell unit above the skirting board, thus avoiding damage from vacuum cleaners or sweep2ng brushes. The extension bracket is a flat plate with a double right angle formed across the middle. One half of the bracket has three clearance holes for wood screws whilst the other has three tapped holes for securing the Part 1/DPL/2270 (mounting plate). Secure the extension bracket to the skirting board with suitable wood screws so that the double right angle across the middle of the bracket positions the upper half of the bracket close to the wall. The mounting plate can now be secured to the extension bracket, with the two 4BA screws and washers using either of the three tapped holes, depending upon the position required for the bell unit.

Call Exchange or Recall Switch
A composite non-locking switch and lever, titled a Switch 30A-1, can be provided on the right hand front edge of the telephone base so that the lever, which is marked CALL, protrudes under the front edge of the telephone case. The Switch 30A-1 and a dummy switch (Part 1/DLE/85) which is fixed to the left hand front edge of the telephone to maintain and aesthetic balance, are packed together and should be requisitioned as a Switch 30A-2. The Switch 30A-1 is held in position by the front bottom edge of the switch case engaging under a slotted projection in the telephone base and a rounded projection on the back of the switch case engaging a sprung lug formed at the base of the dial clamp mounting.

To fit the switch and dummy first remove the telephone case. Present the switch to the slot in the telephone base, with the lever tilted downwards, so that the bottom front edge of the switch case can be engaged under the slotted projection. Apply pressure to the rear of the switch so that it rotates backwards towards its final position. The switch case will audibly snap into its final position. Check that the switch lever is free to operate and restore. The switch leads can now be connected to the appropriate terminals on the telephone circuit board, care being taken that the leads do not foul the cradle switch assembly or the linesman's latch. The dummy switch should be mounted on the left hand side of the base in a similar manner to that described above. To remove either the switch or the dummy, a Screwdriver Inst No. 2 should be engaged, from under the base, between the rounded projection on the rear of the switch, or dummy, and the sprung lug formed on the telephone base. If a steady downward pressure is applied to the switch lever whilst the screwdriver is twisted to disengage the switch or dummy body projection from the sprung lug, the switch or dummy can be pulled clear of the telephone base.

Auxiliary Gravity Switch
A Switch 19A-1, which is a micro-switch with mounting plates and fixing screw, can be secured to the side of the existing micro-switch on the telephone printed circuit board, to provide an auxiliary gravity change-over switch. The Switch 19A-1 should be clamped in position using the screw and tapped plate provided so that the existing micro-switch is sandwiched between the auxiliary gravity switch and clamping plate. When the Switch 19A-1 has been secured and the leads connected to the telephone circuit, check that the leads do not foul the cradle lever and that the gravity micro-switches function correctly.

Bell Cut Off Switch
A Switch No. 35A-2 can be fitted in the bell unit to the two rectangular pillars which rise from the volume control latch plate to provide the bell off facility. The switch is retained in position by the stop screw. The thickness of the switch withdraws the stop screw sufficiently to make the off position of the volume control available to the user.

To fit the switch the volume control stop screw must first be withdrawn and the lever set to loud. Hold the bell unit with the volume control lever pointing towards you. Position the switch such that its operating lever is towards you with the lever pivot to the left hand side. Locate the switch on the moulded pin of the latch plate and secure the switch to the latch plate with the stop screw. Check that all four volume control lever positions can be obtained and that the switch operates when the off position is selected.

Bracket Telephone 18A
This item is a moulded shelf assembly that can be mounted on the Part 1/DPL/2270, (which is used to mount the bell unit) to provide a container for the Bell Unit No. 776 and a rest for the Telephone No. 776. When this bracket is used the bell unit MUST be mounted in it to provide rigidity.

The Bracket Telephone 18A consists of three parts. The body moulding (Part 1/DBR/705), a lid (Part 1/DPL/2269) to cover the bell unit and provide a resting surface for the telephone, and a plug (Part 1/DPL/225). This is used to fill a hold, in the body moulding, which provides access to a Jack 136A. The jack is only required for Plan 4 arrangements and is described later.

To Install the Bracket Telephone 18A It is not necessary to disconnect the cord from either the telephone or the bell unit during installation in the wall mode. No attempt should be made to feed the telephone cord through the hole in the body moulding; this hole is for the insertion of a plug into the jack on a Plan 4 installation. Secure the mounting plate (Part 1/DPL/2270), which is packed with the Telephone No. 776-1, to the wall or other fixture. The mounting plate may be secured to a conduit box but it should be confirmed that the box is secured firmly enough to support the weight of the telephone, bell unit and telephone bracket. A clearance of at least 130 mm (5 inches) must be allowed above the mounting plate which must always be secured with the edge, having the two single thickness projections, at the bottom. The body moulding, with the flat rear surface uppermost, should be raised above the mounting plate and slid downwards so that the webs formed on the sides of the moulding engage with the flanges on the side of the mounting plate, and the bottom edges of the body moulding and mounting plate align. The moulding will now be held firmly, except for upwards movement, by the mounting plate.

Inside the body moulding, at the front, two hook projections are formed adjacent to the edge of the large central hole, and adjacent to the rear edge of the central hole a clip is formed. The two hooks and the clip are used to secure the bell unit, minus cover, within the body moulding in a position with the components facing upwards, bell gongs at the front.

Remove the cover from the bell unit, this item is no longer required and should be returned to stock. Slide the cord grommet out of engagement with the cord anchor block. Then turn the grommet through 90 degrees and re-engage it in the anchor point moulded into the bell unit base. This enables the instrument cord to feed downwards from the bell unit.

The plug (Part 1/DPL/2255) which is packed with the body moulding and the lid, should now be fitted into the hole in the right hand side of the body moulding. The plug should be fitted from the inside, with the flange inwards, and should be a close fit into the body.

The bell unit should now be fitted into the body moulding in the following manner. Hold the bell unit, minus cover, in the hand with the components facing upwards, bell gongs at the front. Turn the bell unit so that the edge containing the cord anchor block is at the bottom. Rotate the bell unit by approximately 45 degrees, clockwise or anti-clockwise, and feed it upwards right through the hole in the centre of the body moulding until it is above and clear of the moulding. Turn the bell unit until the components are facing upwards, bell gongs at the front, and gently place the bell unit inside the body moulding. Raise the rear of the bell unit and locate the front edge under the two hooked projections formed in the body moulding. Check that the instrument cord falls clear of obstructions and then press the rear edge of the bell unit downwards until it is held by the body moulding clip.

Cables can be fed into the bell unit through the slot adjacent to the group of six terminals and terminated as described above.

On top of the lid (Part 1/DPL/2264) is a box formation; adjacent to it, on the rear edge, are two projections and on the front curved edge is formed a clip. To fit the lid, first ensure that the bell unit and body moulding are correctly located. Present the lid tilted downwards at an angle of approximately 45 degrees with the clip highest, to the moulding so that the two projections pass through the two slots in the back of the moulding. Press the front of the lid downwards until the clip engages. This secures the lid. The box formed on the top of the lid fits into a recess formed in the base of the telephone. If the telephone is now placed on the Bracket Telephone 18A it will be secure against accidental displacement.

Jack 139A
To provide Plan 4 arrangements a Jack 139A can be fitted within a Bell Unit No. 776, whether it is wall mounted or contained within the Bracket Telephone 18A. To fit the jack, first remove the bell unit cover, disconnect the instrument cord terminations and then remove the cord anchor block. Secure the Jack 136A in the position vacated by the anchor block, so that the plug can be inserted from the side of the bell unit, and terminate the flexible leads.

When the Bell unit is to be mounted within the Bracket Telephone 18A fit the Jack 139A to the bell unit before the bell unit is fitted into the bracket.

To allow insertion of the Telephone plug, through the body moulding into the jack, the Part 1/DPL/2255 (plug) should be omitted from the bracket.

Plug 420 Grey-5A
To enable the Telephone No. 776 to be used as a portable instrument on a Plan 4 arrangement, recover the instrument cord and replace it with a Plug 420 Grey-5A. (Combined plug and cord.)


Plan 1A
Telephones No. 776 may be used throughout a Plan 1A installation, or in association with other 700 type telephones. When a mixture of telephones is used, the appropriate N diagram will be used for each individual station according to its type.

Plan 4
Due to differences between the wiring of a Plan 4 arrangement using Telephones No. 776, and that using other types of telephone, it is not possible to mix compact telephones with others on the same installation. Thus if a 'Compact' is requested as a portable telephone on an existing system of a different type, the whole installation must be renewed using apparatus listed in the relevant 'Compact' N Diagram.

However if the additional telephone is installed as a fixed station, providing Plan 4 off Plan 1A facilities the two types of telephone will inter-work by wiring each individual station to the appropriate N Diagram according to its type.

Where an installation has to be renewed and only one Compact telephone is charged on the advice note, then Sales Division must be contacted to negotiate the additional charge for the extra Compact telephones required.

Stations can be either a Bell Unit No. 776 with Jack No. 136A or a Jack No. 95 if a bell is not required at that point.

All items thrown spare by modifying the basic telephone should be returned to stock, to be either reissued as maintenance spares or used for local wire up, e.g. instrument cord and bell unit anchor block when modifying for a Plan 4 or bell unit cover and bracket blanking plug when fitting as a wall type.


Dgm N 876 - Connections for Exclusive Service, Shared Service, PBX Extension and details of add-on units.

Dgm N 2801 - Connections for Plan 1A, Exclusive Service.

Dgm N 2821 - Connections for Plan 1A, Shared Service.

Dgm N 2804 - Connections for Plan 4 Exclusive Service.

Dgm N 2824 - Connections for Plan 4 Shared Service.

TI E5 B2771 - Maintenance Instruction.

Jubilee Compact

The compact telephone was first introduced in 1977 as a limited edition in the colour 'Balmoral Blue' to mark the occasion of the Queens Silver Jubilee. This version was known as the Telephone No SA 2/SA 4271-1.

The Jubilee telephone was marketed in two versions, English and Scottish, the differences being the type of royal crest in the dial label centre.

The telephone was later made available as the `Compact' in a choice of three colours (Stone, blue or Brown). It was the first telephone aimed at the residential market. Its compact fore and aft dimensions allowed it to be sited on a narrow ledge such as a window sill. It required a separate Bellset which could also be mounted at skirting level or within a specially designed wall bracket, on which the telephone could be placed. It employed the standard Tele No. 746 circuitry with a new ringer unit, the Uni-coil Bell No. 79 and a Dial No. 21 that was a low inertia version. This ringer then became a component option for the Tele No. 746.



Dgm MS22013 - Connections for Exclusive Service, Shared Service, PBX Extension and details of add-on units.

Dgm MS22014 - Connections for Plan 1A, Exclusive Service.

Dgm MS22015 - Connections for Plan 1A, Shared Service.

Dgm MS22016 - Connections for Plan 4 Exclusive Service.

Dgm MS22017 - Connections for Plan 4 Shared Service.

Additional Information

Tele SA/4271Mk 1yyy1971?Field trial version
Tele SA 4271-1Mk 1yyy Field trail version, combined with B/S SA4271
Tele 1/SA 4271Mk 1yyy Field trial version , with Switch 30A-2
Tele 1/SA 4271-1Mk 1yyy Field trial version, wired for shared service
Tele 2/SA 4271-1Mk 1y  1977Jubilee version - Balmoral blue only
Tele 776Mk 1yyy10/74Released version - no bell, no wall mounting plinth
Tele 776/1Mk 1yyy1/74Complete with bell unit No 776
Tele 776/2Mk 1yyy7/74As 776/1 but with plinth


BACK Home page BT/GPO Telephones Search the Site Glossary of Telecom Terminology Quick Find All Telephone Systems

Last revised: December 02, 2018