TELEPHONE No. 741 & 8741

How to wire your Telephone No. 741 to make it work on Plug and Socket

Click here for Additional Buttons N849 - Web users - CD users.

Click here for the Auxiliary Switches N848 - Web users - CD users.

Circuit diagram N841.

Click here for the circuit diagram - Web users - CD users.

Switches for telephone No. 741

Telephone No. 8741 was introduced in 1981 and fitted with high impedance bell coils and a new style Plug and Socket cord.  These could be found in D, F and G variants.

TELECOMMUNICATIONS INSTRUCTION
C MARKETING
INSTALLATION
3 Internal
B1025
Issue 1, Nov 1972

TELEPHONE No. 741
Description

GENERAL
This Instruction describes the Telephone 741 which is the counter-part of the Telephone 711. The principal changes that have been made take advantage of parts developed for the Telephone 746 and are as follows:-

• All transmission components, including the regulator permanently connected, are mounted on a printed wiring board.
• Use of microswitches for the gravity spring-set. This has necessitated alterations to the brackets and plungers to provide the linkage between plunger and switch.
• A plain outer dial ring matching the telephone cover and used in conjunction with a dial having numbers only on a 'silver' background.

Many parts of the Telephone 741 are identical to those of the Telephones 711 and 746 which are described in B1004 and B1020 respectively. This Instruction describes only those parts which are particular to the Telephone 741. The Telephone 741 is for use in automatic areas only and is suitable for use on lines of up to 10 dB at 1600 Hz with a signalling limit of 1000 ohms loop resistance. It cannot be used on local battery circuits. The telephone can be modified for a variety of uses by the fitting of add-on units, adapters, etc. Early supplies were of the Mark 1 version, which had a metal base. New supplies will be of the Mark 2 version which has a plastic base. This has been designed to provide an improved fit to the wall bracket.

Telephone 741 Grey	Telephone 741 Ivory

ADD-ON UNITS

• Single press-button.  See B1004 and Dgms N841, N848.
• One-to-four press-buttons.  See Bl004 and Dgms N848 and N849 .
• Auxiliary gravity-switch contacts.  These are provided by fitting a Switch No. 19B-1, 19D-1, 19C-1 for one, two or three change-overs respectively.  Linkage to the plunger is provided by a Kit No. 166A.
• Additional 2 pf capacitor.  A Capacitor, Paper, No. 7712-2 and a Clip No. 90 are fitted.
• Additional terminals.  Fit one or two Parts 1/DST/836 (6 terminals) or a Strip, Connection, No. 155A (18 terminals).
• Buzzer No. 32C-3.  Normally fitted on right-hand bracket when required, in an extension telephone on Extension Plan 105 or 107.
• Lamps.  As detailed in B1004 but using a cover Part 4/DCO/659.

Plan views showing positions of auxiliary switches and buzzer

USE WITH PLAN SET N625 (WALL)
The Mark 1 (metal base) telephone has two rubber buffers fixed to the base at the top. These must be removed along with the two feet at the bottom before assembling the plan set. The Mark 2 Telephone has two moulded studs in place of the feet. These must be broken away before assembly to the plan set. When a Mark 2 Telephone is recovered from a plan-set, two rubber telephone feet (parts 2/DBU/259) should be fitted in the holes left, by breaking away the studs before re-issuing the instrument.

PRESS-BUTTONS, HANDSETS, ADDITIONAL WATCH RECEIVER, INSTALLATION
Information given in B1004 applies.

REPLACEMENT PARTS
The Table below lists the replacement parts which are available.

Part - Rate Book description
Cover (without opals) - Part 3/DCO/659, Colour
Special 6BA screw (to fix cover to base Part 1/DSC/176) Long dummy button - Part 1/DBU/271, Colour
Spring clip (for long dummy button) - Part 1/DSP/510 (2 required)
Standard plunger For use with DFR/107 - Part 1/DPL/382
Spring For use with DFR/107 - Part 2/DSP/1507
T Bracket - Bracket, Telephone, No. 16

(Formerly EI Telephones, Stations, A1074)

Additional information

Cases
Original Telephone 711 cases were Perspex (Polymethylmethacrylate, code 12 in the moulding somewhere) but later they were ABS (Code 17 ISTR).

The Telephone 741 case was the almost the same as the 711, except that the 741 version had a rebate about 1.5mm deep and the same wide on the inside edge.  This was all round the face of the body that contacted the chassis. It allowed for the up-turned edge of the metal chassis (originally designed for the 746) to be snugly accommodated.

A 741 case will fit a 711.  The other way round it depends on which variant of the base is being used.  The metal base became rare as it rattled on the Bracket, Telephone,  No. 16.  The plastic bases were proprietary and different moulders had subtly different designs.

Paul Ebling

Last revised: April 06, 2010