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SQUIRT transmitter
Rod-based burst encoder - this page is a stub

SQUIRT was one of the first attempts to create a device for sending messages in morse code at very high speed in order to minimise the chance of detection and location by means of Radio Direction Finding (RDF). It was developed in the UK during WWII for use by the SOE and SIS [1].

The device consisted of a number of field-configurable rods that were mounted in between two end-pieces or brackets. Each rod consisted of a number of conducting and non-conducting elements that together formed the dashes and dots of (part of) a morse coded message [1].

The non-conducting parts were made of black bakelite, whilst the conducting elements were probably made of brass. A total of 18 rods could be constructed this way. Once the message was complete, the relevant rods would be mounted in between the two end-brackets, and a wiper contact — connected to the transmitter's morse key input — was used to play back the message, by wiping over the rods at a constant speed.

SQUIRT was supplied in two metal containers — marked A and B — one of which is shown in the image on the right [1]. The full contents of each container is listed and described in the original wartime Operating Instructions [A].

It is rumoured (but not confirmed) that SQUIRT was never used in an operational context, due to the lack of recording and decoding equipment. This seems strange, as the British had access to tape and wire recording devices, and could even write morse code signals onto paper strips with an undulator. 1 It seems far more likely that it was simply to large and cumbersome to use.
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SQUIRT was not the only attempt to create a morse burst transmitter during WWII. It is known, for example, that the Polish Radio Service in England created TELMA, a device that could read morse code from a printed paper strip and transmit it at high speed. At present, no further information about SQUIRT is available. Any further information and photographs would be much appreciated.

  1. During WWII, undulators were used by the British to record the characteristics of hand-generated morse code signals, in order to determine the identity of the operator, in the same way as with handwriting. Not to be confused with a modern high-enery physics insertion device, which is also known as an Undulator.

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  1. Squirt transmitter, operating instructions 1
    Unknown author. Date unknown.
  1. Document kindly provided by Louis Meulstee [1].

  1. Louis Meulstee, Wireless for the Warrior, volume 4 — Squirt
    ISBN 0952063-36-0, September 2004
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Crypto Museum. Created: Saturday 17 August 2019. Last changed: Wednesday, 02 September 2020 - 12:56 CET.
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