M 0026

For Disabled Users of Telephones in Automatic Areas

This Instruction describes the Sender No. 1 and its operation, indicates the circumstances in which it should be used and details the method of connection to the telephone.

Purpose and Use
The Sender No. 1 has been designed so that by pressing a button, a physically disabled subscriber may gain access to the assistance operator who would normally only be available by dialling 0 or 100. The subscriber lifts the handset from the telephone, waits for dial tone and then presses the start button on the sender which dials 0 or 100 as required. A request for the installation of the sender will normally come from the Sales Division who will have instructions issued by the I.T.D., but the guiding principles are as follows:-

  1. If the disabled user lives alone, the P.O. should choose the least expensive method of providing disabled subscribers service.

  2. When the disabled user lives with an able bodied person it should be the normal practice to provide a Sender No. 1. The able-bodied person can then dial calls in the normal way.

  3. Retrospective changes should only be made when a genuine economy or service improvement [as in (b)] will be effected, e.g., an exchange relayset providing service for a user living alone should not be thrown spare and replaced by a Sender No. 1 simply because the Rate Book value of the former exceeds that of the latter.

Senders No. 1 are produced for the Post Office by more than one manufacturer and hence vary in detail but all consist of an electrically driven pulse wheel which can be arranged to send 0 or 100 as required. It is brought into use by pressing a start button; a relay which is included in the circuit locks the sender on after a brief depression of the button, while, at the same time, the circuit arrangements ensure that the sender goes through only one cycle of operation even if the start button remains depressed. Mechanically operated off-normal springs are fitted which are operated from the pulse wheel for the duration of dialling. The sender is powered by a separate 9V battery, three Batteries, Dry, No 11 can be used. The Sender is housed in a metal case approximately 6in x 4in x 3in deep, having a grey hammered finish, with the start button protruding at the top. The device may be stood on a desk or wall mounted and is connected to the telephone by a flexible cord.

Circuit operation
The internal connections of the sender are shown in Diagram N681. Diagram N2307 shows the connection of the device to the telephone. The user lifts the receiver, waits until dial tone is heard and then presses the start button momentarily. This causes relay R to operate and lock itself via R1 operated, MS1 normal. R1 also connects the battery to the motor which commences to drive the pulse wheel. The off-normal contacts ON1 and ON2 operate to short circuit the receiver and provide a clean loop for dialling. The pulser contacts are then opened and closed by the pulse wheel and dial pulses are sent to line. At the end of the pulse train the microswitch MS is operated. MS1 changes over and relay R will release, assuming the start button has been released earlier. MS2 changes over and continues to drive the motor via R1 normal until the microswitch restores to normal again when the pulse wheel is in its home position. Should the start button be held down by the user during the whole of the pulsing train, relay R remains operated and when MS2 changes over, the motor drive is disconnected and the pulse wheel comes to rest a few degrees short of its home position. When finally the button is released the motor drive circuit is re-established via MS2 operated, R1 normal, until the home position is reached when the microswitch restores.

The call is now completed via the operator and the sender. is ready for a further call.

The sender is adjusted to send 0 or 100 by the movement of a masking plate attached to the pulse wheel. The masking plate may be moved and refixed in a position where it prevents the operation of the pulser contacts by the pulse wheel when in the position in which '1' and the first 0 would normally be sent. When the mask is correctly positioned it must be locked by securely tightening its fixing screws. If the '100' code is required the mask should not be removed from the pulse wheel but should be left in its inoperative position in case the sender is required to revert to the 0 code later.

The motor governor is effective in keeping the speed sensibly constant over a battery voltage range from 9.0v to 7.5v. The rectifier in the battery feed prevents the motor driving in the reverse direction, which could damage the governor; for the same reason the pulse wheel must not be turned by hand.

Method of connecting Sender No. 1
The sender may be associated with any 200, 300, or 700 type telephone from which an assistance operator can normally be obtained by dialling '0' or '100'. The pulser contacts of the sender are connected in series and the off-normal contacts of the sender in parallel with the corresponding contacts of the telephone dial.

Diagram N2307 shows the connection of the device to the telephone. Particular attention is drawn to the extra wiring required in the telephone between the dial off-normal springs and the spare terminal on the telephone connection strip. An external start circuit can be provided in exceptional circumstances by the use of a Press-button G and the S and terminals.

Only one sender should be provided on extension plan arrangements as the sender may be operated by a Press-button G at the extension instruments. In these instances spark quench components must be fitted locally in accordance with Diagram N2307, panel 7.

Previously E.I. Telephones, Stations, G3102.

A PP3 battery would normally be fitted inside the case.

Circuit diagrams - N681 and N2307.

Drawing - CD1688.

Specification - S655.

Introduced in 1960.  Prototypes were made by Burgot Rentals Ltd.

Superseded by the Autodial No. 401.

POEEJ article - 1962.


Additional Pictures
Internal Views


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Last revised: January 21, 2024