TELEPHONE No. 746 & 8746

Switches for Telephones
Model types
Telephone No. 8746 - Telephone No. 746 modified for PST working with plug ended line cord
General Information on 700 Type Telephones
700 Type telephone circuit description
700 Regulator operation
How to wire your Telephone No. 746 to make it work on Plug and Socket
How to remove the case
Dismantling a Handset No. 3
Restoring the plastic cover and handset
Identifying the component parts on the circuit board
Click here for the later variant with bell volume control and Unicoil bell
Click here to hear a Telephone No. 746 bell ringing
Click here for the colour range
Colour samples

Diagram for Additional Buttons - N849.

Diagram for the Auxiliary Switches - N848.

Diagram for the telephone circuit diagram - N846, SA 10011 (Telephones No. 746R and 8746) and SA/SAW 102180 (Telephone No. 746C).

Specifications - S1404 and S1405.

Drawing - 92773, 92773/0/5, 92773/1/1, 92773/1/2, 92773/1/3.

Cut-away picture of a Telephone No. 746 with the later case
The case has a recess for the handset to sit in

Mark 1 model - note sloped case under handset Mark 1A model - note recess in top of case for handset

In 1967 the 746 Type telephone was introduced (See also Telephone No. 736).  This was an improved version of the 706 range and offered similar facilities.  The case styling is slightly different from the Telephone No. 706 although it retains the same overall look.  The case now has an integral handle which obviates the need for a separate handle (the Telephone No. 706  plastic handles tended to break).

Unlike the Telephone No. 706, this phone could also have two switches fitted.  The oblong dummy plate above the dial is removed and a single or two half size transparent plastic buttons could be installed. 

Originally the case on the "Mark 1" telephone (Part Number 1/DCO/718) had a slope from above the dial, sloping backwards, under the handset, finishing at the raised handset stops to the rear of the case.  This design was found to allow the handset to sometimes slide forward and this was sometimes enough to allow the switch hooks to operate - thus leaving the phone off hook.  The case was later modified on the "Mark 1A" telephone (Part Number 2/DCO/718) and the handset now rests in a recess, with raised sides to stop the handset sliding forward.  The pictures above show both the early and later style cases.

Inside the circuitry is different in that the regulator components are soldered directly onto the printed circuit board, the switch-hooks and other components were miniaturised.  No conventional wiring version was produced.  The same colour options as for the Telephone No. 706 were offered to the customer.

The Telephone No. 746 was later produced with the new style plug type lead (PST and renumbered as the Telephone No. 8746) and converted to high impedance bells (two, 2000ohm ringer coils).

A dark brown version was introduced and Telephone No. 746 range which was marketed as the 'Yeoman '.

Removing the case is via a single self retained screw on the rear of the case.  Undo the screw until it goes slack - do not remove the screw completely!  Do not remove any of the screws in the base unless you wish to remove the bell gongs and bell ringer.

Available to all customers in 1970 and supplied into the late 1980's as maintenance stock.

Later phones and refurbished phones had the carbon Transmitter No. 16 replaced by the electronic Transmitter No. 21 (blue or red variants) due to transmitter noise issues.

Telephone No. 746 when used on the Plan 4 system

A 1076
Issue 2, Feb 1969


This Instruction describes Telephones No. 740 and 746, which are counterparts to the Telephones No. 710 and 706 and have been developed from the printed wiring version of the Telephone No. 706.  The principal new features are as follows:-

  1. A new design of telephone cover, which now incorporates a carrying- handle.

  2. Use of microswitches for the gravity spring-sets.

  3. Smaller electrical components, with the regulator permanently connected.

  4. Optional provision of one or two press-buttons on the Telephone No. 746.

  5. A common chassis for both types of telephone.

  6. A plain outer dial ring matching the telephone cover and used in conjunction with a dial having numbers only on an antique silver background. (During the transition to all figure numbering some telephones may be issued with an outer dial ring, having numbers and letters, which matches the handset.)

Many parts of the Telephones Nos. 740 and 746 are identical with those of the Telephones Nos. 710 and 706 which are described in A1063 and A1060 respectively.  This Instruction describes only those parts particular to the Telephones Nos.740 and 746.

The telephones, which as issued are for use in automatic areas only, are suitable for use on lines of up to 1000 ohms T.E.R.

The telephones can be modified for a variety of uses by the fitting of add-on units, adapters etc. and these will be described in later instructions.

The Telephone No. 746 is available in black, blue, two-tone green, two-tone grey, ivory, red and yellow. The Telephone No. 740 is available in black, two-tone grey and ivory only.

On both types of telephone the cover is secured to the telephone assembly by a lug on the front skirt which engages in a recess in the leading edge of the base and by a single fixing screw located above the cord entry at the rear of the case.  The screw, which is held captive by a bush and a spring, engages in a tapped hole in the cord clamp, a T-shaped metal bracket riveted to the rear of the base.

The telephones, as issued, have the aperture for the press-button(s) closed with a dummy button held in place by a clip.  When a press-button unit is fitted the dummy button and clip should be secured within the telephone for subsequent refitting.  A phone with the single switch is shown to the right.

The outer dial ring fits round the hole in the sloping face of the cover through which the dial protrudes.  The dial ring is secured by dropping the lugs on the ring into the recesses provided on the edge of the hole in the case and turning clockwise until the two recesses provided for the finger-stop line up.  To remove or refit the ring the cover must be taken off the telephone assembly.

An 'off-rest' position is provided with the handset resting across the instrument just above the dial.

A carrying-handle, in the form of a recessed finger ledge, is provided between the horns directly below the normal handset position.

Telephones Nos. 740 and 746 are fitted with a base made of mild-steel with a crackle black-enamel finish.  There is a 'knock-out' and three holes in the base for use with a Plan-set N625 and a cord-entry hole at the rear of the base for a watch receiver, as on the Telephone No. 706. A ring of slots is punched out beneath each of the bell gongs.  Two studs, fixed to the base, support the printed wiring board which is secured by a single screw inserted into a tapped hole raised in the base.  The bell gongs are supported by two removable moulded pillars; two long screws pass through the metal plate supporting the dial, the gongs and the moulded pillars into tapped holes raised in the base.

The plunger-supporting brackets are riveted to the base.

Printed wiring board
The main features of the printed wiring board are:-

  1. its reduced size

  2. the regulator is permanently wired in

  3. the gravity microswitch is permanently wired in.

The printed wiring board is located by mating slots in the front edge of the board and in the sides of the plunger-mounting bracket.

The regulator is an integral part of the telephone circuit and provision is not made to render it inoperative.

The gravity spring-set consists of a microswitch positioned alongside the left-hand support of the plunger-mounting bracket.  The switch is operated by a lever pivoted on a bracket at the rear edge of the switch cover, the upper end of the lever being formed into a channel in which a projection on the plunger assembly rides.  A coiled spring holds the lever in position.  The switch is operated when the handset is on the rest.

When the case is removed the switch can be locked in the off position.  The switch hook is manually lowered and the swinging latch arm, which is fixed towards the top of the switch hook mounting, is lifted so that it locates against the front of the arm.  Once pressure on the switch hook is removed the latch will be held in place by friction.  Pressing the switch Hooks slightly will release the latch.

Dial and dial cord
The telephones are fitted with a Dial, Automatic No. 21FA (clear).  This has a number ring with black figures on an antique silver background and a transparent finger-plate.  The dial cord has spade-tags at one end for connection to the dial terminals and ring-tags at the other for connection to the telephone terminals.

Terminal block and line cord
The Telephone No. 746 is supplied with a four-wire line cord and a four-way terminal block, the Telephone No. 740 is supplied without line cord or terminal block.

A single-coil bell is under development for the Telephones Nos. 740 and 746, but early issues will be fitted with a Bell No. 59C-1.  The bell is screwed to the base of the telephone.

Telephone circuit
The circuit for Telephones Nos. 740 and 746 shows one change from that of the Telephone No. 706.  The brown wire from dial terminal D3 is taken to telephone terminal T3 instead of gravity spring 5.  This short-circuits the transmitter when the dial is taken off-normal and prevents surges in the spark quench circuit passing through the transmitter.

Press-buttons and switches
The press-buttons for use with Telephones Nos. 740 and 746 are transparent to obviate the stocking of a range of colours for each type of button and legend.  The legends available for each type of press-button are shown in Diagram N849.

Press-buttons for the Telephone No. 740 are provided by removing the dummy button and fitting a Part 1/ ... 10/DBU/372 using the pin, Part 1/DPI/203, provided in the telephone.

A single press-button for the Telephone No. 746 is fitted by removing the dummy button and clip and inserting a Part 1/ or 2/DBU/362 which is retained by two pins, Parts 1/DPI/203.  When two press-buttons are required, two Parts 1/ ... 6/DBU/363 are fitted, each with one Part 1/DPI/203.

Where a single change-over contact (non-locking) is required in association with a press-button in either telephone a Switch No. 5A-4 together with an operating plunger, Part 1/DPL/1022, is fitted.  Other non-locking contact assemblies can be provided on either telephone by fitting the spring-sets described in Diagram N848 together with a Part 1/DPL/1022.

There a locking single change-over contact is required in association with a, press-button on either telephone a Switch No. 5A-9 is fitted (this switch includes an operating plunger and is now superseded by Switch No. 23A).  Other locking contact assemblies can be provided on the Telephone No. 740 by means of the latch-plate as described in A1063 and Diagram N848.

Additional gravity switches can be fitted to either telephone when required as follows:-

A single change-over  Switch No. 19B-1
Two change-overs  Switch No. 19D-1
Three change-overs   Switch No. 19C-1

Replacement parts
Table 1 lists the replacement parts which are being made available:-


Part To be requisitioned as:-

Cover (Telephone 740)  Part 1/DCO/723 (colour)
Cover (Telephone 746)  Part 1/DCO/703 (colour)
Outer dial ring  Label No. 479A
Buttons (feet)  Part 2/DBU/259
Dial  Dial, Automatic No. 21FA (clear)
Handset  Handset 3 (colour)
Mouthpiece  Mouthpiece No. 21 (colour)
Earpiece  Earpiece No. 26 (colour)
Transmitter  Transmitter-inset No. 16
Receiver  Receiver-inset No. 4T
Transmitter spring  Part 1/DRI/50
Receiver spring  Part 1/DRI/50
Bell  Bell No. 59C-1 unmounted
Bell gongs  Bell-gongs No. 24A and 24B
Link (for telephone terminal strip)  Part 1/DLI/20
Links (for terminal block)  Parts 1/DLI/19 and 1/DLI/29
Terminal block (Telephone 746 only)  Block, Terminal No. 52A
Handset cord  Cord, Instrument, 4/88AK (colour)
Line cord (Telephone 746 only)  Cord, Instrument, 4/83AA (colour) 72 in.
Dial cord  Cord, Instrument, 5/42L
ThermistorThermistor 1A-1
Printed wiring board with components  Telephone-unit D 92732

References:- A1060 & A1063

How to remove a Telephone No. 746 or 740 case

  1. Locate the single case fixing screw on the rear of the case, just above the cords.
  2. Slacken the screw until it becomes loose - it remains fixed to the case, held by a spring and is not completely removed.
  3. Lift the rear of the case upwards and towards the front of the until it is clear of of the dial.
  4. Pull front edge of case forward to release from lip on front of base plate.

Re-fitting is the process in reverse, except you may have to slide the casing dial ring to locate it over the dial.

If the casing screw does fall out - fit back as follows:-

  1. Place spring on screw.
  2. Insert screw, complete with spring, into hole in case.
  3. Offer up nut with threaded end towards the case.
  4. Screw the screw into the nut, until the threaded section is free.

This picture shows the later style of auxiliary switch installed correctly This picture shows a standard telephone 

Additional information

ModelMarkBlackGreyIvoryRedYellowGreenBlueBrownIntroduced Remarks
Tele 746Mk 1 yy yy yy y    
Tele 746Mk 1A yy yy yy y    
Tele 746Mk 2 yy yy yy y    
Tele 746AMk 1  yy     2/73 Ivory introduced 1/76
Tele 746BMk 1 yy yy yy y 10/78 Not preceded with 5/79
Tele 746BMk 2 yy yy yy y   Adjustable bell 59A
Tele 746BRMk 1 yy yy yy y 12/78 ELR button & bell 79A
Tele 746BRMk 2 yy yy yy y  12/78ELR button & bell 59A
Tele 746CMk 1 yy yy yy y 9/79 Used micro-circuit D4529
Tele 746CRMk 1  y      9/79Tele 746C with ELR
Tele 746DMk 1 yyy yyy y 1/80High impedance bell
Tele 746FMk 1 yyy yyy y   
Tele 746FMk 1A yyy yyy y   
Tele 746FMk 2 yyy yyy y   
Tele 746FMk 3 yyy yyy y   Single Uni-coil bell
Tele 746FMk 1  yy      Refurbished
Tele 746FMk 2  yy      Refurbished
Tele 746LMk 1 yyy yyy y   
Tele 746RMk 1  yy     8/73 
Tele 746RMk 1A  yy     9/73Part No 3/DCO/703
Tele 746RMk 2  yy       
Tele 746RMk 1  yy      Refurbished
Tele 746RMk 1A  yy      Refurbished
Tele 746SMk 1        5/79Field trail (Survey 42)
Tele 746SRMk 1        7/79Field trial (Survey 42)
Tele 746TMk 1  yy     9/79Obsolete 3/83 (Plessey)
Tele 746WMk 1  yy     2/73Field trial control item

The Telephone No. 8746 can be found in C, D, F, G, GR and R variants.  The GR and R variants were fitted with Earth recall switches.  All these models date from 1981 onwards.  Specification - S1481.

Every variant was available in the seven standard colours except for the F and G variants which were also available in Brown.

The Telephone No. 8746C still retained the 1000 ohm bell but was fitted with a Telephone Unit D94244.

Telephone No. 8746D was fitted with a 4000 ohm bell and the Telephone Unit D94244.

Telephone No. 8746F has a Bell 59C-1 (1000 Ohm D.C. Resistance).
Telephone No. 8746G has a Bell 59D-1 (4000 Ohm D.C. Resistance).


Telephone SA 4284

Telephone SA 4284 is a Telephone No. 746 used for Teleprax working.  The Telephone No. 746F is modified for buzzer calling and 6v working.

Tele SA4284Mk 1  y  yy yy 11/72Teleprax working


Additional Pictures
These pictures are from 1967 and show an early version.
The bell gongs shown were never used. 



Telephone No. 746 in brown - Yeoman (late 1970's)


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Last revised: February 18, 2023