TELEPHONE No. 765 & 8765

Introduced in 1977 this was a second generation, wall mounted, battery keyphone.

Circuit diagram - N865.

Specification - S975.

Superseded by the Telephone No. 755.

Telephone No. 8755
In 1982 the Telephone No. 8755 Ivory and Grey was introduced and this fitted with high impedance bell ringer and a new style Plug and Socket cord (Cord Connecting No. 4/502 250mm).

This telephone was effectively a recycled Telephone No. 755.

3 Internal

Wall Mounted Push-Button Telephone

This instruction describes the Telephone No. 765 and outlines its application and installation. The Telephone No. 765 is based on the Telephone No. 1/764 and is available in ivory only.

The Telephone No. 765 differs from the Telephone No. 1/764 as follows:-

  • The Keypad and escutcheon plate are inverted.
  • A chromium plated metal handset rest is fitted.
  • A BRACKETS, TELEPHONE No. 16 is supplied with the instrument.
  • The instrument is not fitted with a line cord.
  • The fixing of the pulsing relay has been moved through 90 degrees.

The electronic circuit is powered by a rechargeable nickel-cadmium battery (Battery secondary No. 22) which is not issued with the telephone. Plugs and sockets are provided to connect the battery to the telephone. To facilitate correct identification Battery secondary No. 22 is housed in a red plastic case and the base of the Telephone No. 765 bears the legend:- USE BATTERY SECONDARY NO. 22

The battery may be charged from the line while the telephone is "on-hook", or from a Power Unit No. 53 where line charging is not possible - see Diagram N 865 for details. When the battery is line charged, a charge switching unit (CSU) is incorporated to disconnect the charging circuit during periods of line testing.

With the addition of auxiliary apparatus, as required, the Telephone No. 765 is suitable for use on Exchange lines (exclusive and shared), PBX extensions (with or without recall) and those extension plan installations which could otherwise be met by the provision of Telephone No. 746, except for the following:-

  • Extension Plan 4.
  • In conjunction with Lamp Signalling Units Nos. 1 and 2.

If a Telephone No. 765 is required on an extension plan where pre 700 type telephones exist, other than on the extension plans 5, 5A, 7 and 7A using Bellset 20, 39 or 44, all earlier types of instrument must be replaced by 700 type.

Charging over Exchange lines or 50v PABX extension lines, may be employed for one Telephone on Exclusive DEL and Extension Plans on the following:-

  • DEL
  • Plan 1A - Main or extension

Shared Service Lines and Extension Plans Charging facilities are dependent upon the calling equipment used in the exchange:-

  • Uniselector per line, 200 pt line finder, UAX and TXK calling equipment's allow line charging for only one Telephone No. 765 on each party.
  • 50 Pt line finder, TXE2 calling equipment's restrict line charging to only one Telephone No. 765 to one party only.

Subject to the two points above, the following application may be met:-

  • Shared service exchange line
  • Plan 1A - Main or extension

50v PABX direct extensions and associated extension plans excluding PABX 1 extensions arranged for direct extension night service, line charging may be employed for not more than one Telephone No. 765 (per extension line) on the following:-

  • Direct extension
  • Plan 1A - Main or extension

Charging from Existing Local Power Supply

This method should be adopted for:-
Main of Plans 105, 107, 105A and 107A; two additional connections are required to extend the 12v supply from the Plan-Set N625 to the charging circuit of the telephone.

Charging from Power Unit provided for this purpose except for those that are powered from an existing supply, all other applications will require the provision of a power unit. In addition, a power unit must be provided in lieu of the line charging, when switching facilities are provided to divert the line from the telephone to other equipment. Power Unit 53 should be used and, if required, up to 80 keyphone batteries may be charged from one power unit, however it is recommended that NO MORE THAN 10 BATTERIES be charged from a single fused outlet. An instrument cord with extra conductors and a larger block terminal than that shown in the appropriate N diagrams may be required.

Connection of Telephone No. 765 to ARD 561/7 and ARD 562/7 type PABX's A separate power supply must be provided when this instrument is connected to either of the above PABX's. This precaution is necessary to prevent the line current drain, that occurs when the instrument is 'on-hook' (charging) being detected by the PABX equipment as a permanent calling condition fault.

Telephone No. 765 will accept the same auxiliary units as Telephone 746 (see Diagrams N848, N 4700) with the following exceptions:-

(a) A maximum of 2 auxiliary gratuity switches may be provided.

(b) Lamp Signalling Units Nos. 1 and 2 cannot be provided.

(c) A maximum of 6 additional terminals may be provided i.e. one PART 2/DST/836.

HOOKS, RECEIVER AH is used when RECEIVER, WATCH NO 8T is fitted.
When CLIP No. 90 is required it should be fitted in the normal position.

Extension Plan 105, 105A, 107 and 107A to Diagrams N 4647 and N 4649.
This instrument can be used as the MAIN provided the extension plan is converted to 2wire working using UAA 96.

Extension Plan 105 and 105A to Diagram N 4547 and N 4647.
This instrument cannot be used as the 'B' end extension telephone.

Fitting Remove the screw from the 'T' bracket and fix the bracket to the wall. Slot the Plan-Set N 625 onto the `T' bracket lugs and secure using the 'T' bracket screw through the Plan-Set back plate to the 'T' bracket captive nut. Remove the telephone case, its four rubber feet and the rubber cord entry blank. Using the three Plan-Set screws fix the telephone base to the Plan-Set, having first fed the Plan-Set cord into the instrument.

To make a call, lift the handset and on receipt of dial tone, key in the number, one digit at a time. It is not necessary to pause between key operations while a digit is pulsed out, unless an access digit is keyed, in which case secondary dial tone must be obtained before proceeding.

For information see Diagram N865.

When Power Unit 53 is required it should be installed in accordance with C3 Q0020.

Ensure that the handset is replaced on the rest to prevent excessive battery drain.

The pulsing of Telephone 765 is identical to that of a normal dial telephone and can be tested for speed and ratio in the normal manner. Tests should be carried out when commissioning keyphones to ensure the correct pulsing out of all digit buttons.

When Keyphones are required on either the physical or carrier circuits of 1 + 1 Carrier it will be necessary to provide a Power Unit.

Advice Notes should be checked by Distribution Officers before issue to installation staff in order that arrangements can be made for a power point to be available.

Recovered instruments must be returned to Section Stock. Batteries Secondary No. 22 should be removed from the instruments and handed to stores staff for recharging in Dispenser No. 4A.

Telephone No. 8765 was fitted with high impedance bell coils and a new style Plug and Socket cord.

To change between the different methods of battery charging, straps within the telephone must be moved.  The telephone is supplied with the Battery strapping set to Line charging.  The straps are set T26 - T27.

For 50v local power feed - run the power to the telephone, remove strap from T26 - T27 and strap across T27 - T28.
For 10v local power feed - run the power to the telephone, remove strap from T26 - T27 and strap across T28 - T29.

Line charging

To check the charging circuit connect a milliameter in place of the strap T26 (-ve) and T27 (+ve).  With the handset on the rest a current of 2 - 3mA should flow after 30-100 seconds.  Replace strap after testing.

Charging by local PSU
To check the charging current connect a milliameter in place of the strap T27 (+ve) and T28 (-ve) for 10v PSU's or T29 (+ve) and T28 (-ve) for 50 v PSU's.  With the handset on the rest the current flow should be 2 - 3mA.  Replace strap after testing.

Additional information

ModelMarkGreyIvoryIntroduced Remarks
Tele 765Mk 1yy7/77 GEC uses PBU No 5A/1
Tele 8765Mk 1yy 4/82 GEC uses PBU No 5A/1


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Last revised: February 25, 2021