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 Post Office Equipment for Radar

The Problem.

The message to be transmitted to the filter room was of the form of 10592 AB123C XY1234 N12 46 where

10592 was the time in hours, minutes and tenths of minutes.
ABJ23C was the raid designation for the raid under consideration.
XY1234 was the map reference.
N was the type of aircraft, i.e. hostile or friendly.
12 was the number of aircraft.
46 was the height in thousands of feet.

With the spoken message the time and raid designation were a matter of paper record only. The remainder of the information was given on the calculator display.

The following requirements had to be met

(a) The provision of timing equipment and a means of injecting the raid designation into the recorder.
(b) The provision of equipment capable of converting the time, raid designation and calculator display into a form such that automatic control of a standard teleprinter could be effected.

An additional condition, which was covered by the use of a standard teleprinter, was that it should be possible at all times to send a message by manual operation.

Circuit Principles.

The principle used was to cause conditions to be applied to the banks of a motor uniselector, in accordance with the message to be transmitted, and by rotation of this uniselector to apply earth pulses to a remote control unit, which in turn operated the teleprinter.

A simplified schematic of the arrangement is given in Fig. 4. The timing element was produced by an arrangement of uniselectors controlled from a Clock No. 46. The raid designation was recorded by the insertion of lettered plugs into a jack field, the plugs being strapped internally such that a different condition for each letter or number could be applied to the banks of the send switch. The calculator display lamps were wired direct to the banks of the send switch.

The send switch commenced rotation as soon as a calculator display was set up. In accordance with the markings applied to the selection arcs of the bank, so pulses were transmitted to the remote control unit, thus operating the appropriate teleprinter keys.

The recorder equipment, consisting of five 24-way relay sets, three Siemens motor uniselectors, five standard uniselectors and a test panel, was mounted on an auto apparatus rack 8 ft. 6 in. by 2 ft.

The remote control unit is shown in Fig. 5. The unit consists of a group of electro-magnets designed to mount over the keyboard of a Teleprinter No. 7B, so arranged that plungers associated with the magnets operate the teleprinter keys. The silence cover, specially designed to reduce noise in the operations room, is also shown.

Height Signalling Equipment

This equipment was designed for use at interception stations, where a control officer had to guide fighter aircraft so that they could make contact with enemy raiders. The information which the controllers used in giving directions to the fighter pilot was derived from two sources, namely, (a) a plan position indicator (P.P.I.) showing on a cathode ray tube the range and bearing of the fighter and raider with respect to the control station, and (b) a height finder, from which heights of aircraft were given. The controller was able to observe the P.P.I. display directly, but the height finder was necessarily located in a different part of the operations room.


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Updated 06/11/2001

Constructed by Dick Barrett

Email: editor@ban_spam_radarpages.co.uk

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ęCopyright 2000 - 2002 Dick Barrett

The right of Dick Barrett to be identified as author of this work has been asserted by him in accordance with the Copyright, Designs and Patents Act 1988.