The following article was kindly supplied by Martin Swift G4NCE and originally appeared at his site www.greenradio.co.uk

Below is a copy of the original description of what must have been one of the first,

(if not the first *) police wireless schemes in the UK.

* If you know different, please email webmaster@channel-two.org

BRIGHTON POLICE POCKET WIRELESS SET

The Brighton Police Wireless Scheme was first commenced on 22nd January, 1932,  when a 100 Watt

transmitter operating on a frequency of 147.8 metres (2030 Kcs) and manufactured by Plessey was

installed in the Town Hall at Brighton. Various teething troubles were overcome and on 14th September,

1933, the Pocket Wireless Receivers were brought into general use for patrol constables. The pocket

set  was of the one valve type consisting of two pieces of apparatus, the receiver and the earphone. The

 former contained the dry battery and the accumulator, while the latter incorporated the calling device.

 A length of cable to which was attached a plug connected the two parts. The overall weight was under

 four pounds.

The receiver was carried in one pocket and the earphone in another. The bell on the earphone unit rang

when the transmitter was switched on. Taking the earphone from the pocket, the constable pressed a

small knob at the side and listened for the voice of the operator. This calling up device was the

important feature of the set as it had the effect of making the instrument like a telephone. The sets were

capable of receiving messages at a distance of about six to seven miles from Headquarters. There were

thirty sets in daily use.

The primary advantage of the pocket radio system was that messages could be passed quickly, thus

enabling the man on the beat to act immediately.

Technical Description

The pocket wireless set was constructed in two parts:-

(1)     A bakelite box 6 1/2" by 4 3/4" by 1 3/8" containing the receiver itself and LT and HT.

(2)     An aluminium case 6 3/4" by 4 3/4" by 1 15/16" by 1 3/8" containing telephone earpiece, bell

and relay. Attached to this portion was the three wire cable  which plugged into the set portion

and "switched on" the receiver. The weight of the complete apparatus was about 3 1/2 pounds.

The receiver had one valve, using a Hivac "XL" filament, consumption .067 Amp. The circuit was

an Armstrong super-regenerative and tuning was by a preset condenser, reaction was adjusted by

varying two coils 3/4" diameter, both aerial and reaction coils wound with 90 turns of 32 gauge

double silk covered wire. The aerial consisted of 8 to 2 turns of 32 gauge D.S.C. or enamelled

wire wound in a shallow groove around the edge of the receiver.

Operation of relay and calling up bell

The bell circuit was connected to the L.T. battery, in parallel with the valve filament and across two

adjustable points in the relay. The anode current flowing through two moving coils in the relay tended

to pull the adjustable contacts apart, they being adjusted to a distance of 1/8". When the transmitter

was switched on, the reception of the carrier wave caused a reduction of anode current (normally

approximately .25 of a milliamp) by about 25%. Due to this reduction, the adjustable contacts in the

relay fell together closing the bell circuit. In order to listen in, the user of the receiver pressed a button

switch which again broke the bell circuit. On the cessation of the transmission, the anode current rose to

its former value, pulling the adjustable relay contacts apart and breaking the bell circuit once more.

The valve was of the bayonet type, connections being soldered to it. This was found to give less trouble

than the pinned type used in a valve holder.

The box portion of the receiver was provided with a lid, secured by four spring clips and was easily

removed for the purpose of changing batteries, examining and repairing the set.

Sorry but we have no photographs of the apparatus at present. Can you help?