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R-353 Burst Encoder
The burst encoder described on this page was used exclusively with the Russian R-353 spy radio set. A small unit with a telephone-style dial was used to (passively) record messages on a metal tape, unlike its predecessor, the R-350 which used a photo film roll.
 
A complete unit consists of the recorder with a telephone-style dial and a separate cassette with a metal tape. Both units are normally packed in some kind of 'rain coat' to protect them against rain and dirt.

Inside the recorder is a rotating disc with magnets that act as a recording head, similar to the head of an old-style tape recorder. The head is further protected by a metal lid, that can easily be removed. Inside the lid is a small pen that is used by the operator to enter numbers using the dial.
  

After unpacking the cassette from its raincoat, it can be attached to the recorder. The operator then uses the pen to enter the pre-coded message as a series of numbers (0-9). The pen is entered into the corresponding hole in the dial and then used to rotate the disc until the pen is block by a small metal bracket. The pen is then pulled out, so that the dial can return to its default position. Exactly like you would dial a number on an old-style telephone.

When returning to the default position, the metal tape is advanced sligtly, whilst a digital code is recorded on the tape by the rotating magnets inside the recorder. The advantage of this system is that it requires no batteries.
 
In practice, multiple cassettes would often be issued with each radio set. A secret agent would use the dial to record a pre-coded message onto the tape. He would then hide the tape in a pre-determined place, a so-called dead drop, where he would find a new - empty - tape.

The tape was picked up later by the radio operator, who would take it home and attach it to the R-353 transmitter. After establishing contact with the East-European head office, the message would then automatically be played back at very high speed (burst) to minimise the risk of detection.
  
Click the image to view the R-353 radio set

The advantage of using a dead drop was that agent and radio operator didn't have to be aquinted, minimising the risk of compromise when the other person was exposed. In certain situations, the R-353 was also used directly by agents themselves to send messages home. In those cases, agent and radio operator would be one and the same person.
 
Recorder, cassette and pen Recorder and cassette packed in their raincoats Recorder and cassette after unpacking Close-up of the recorder (dial) Close-up of the cassette with a plastic cap to protect the metal tape The pen stored inside the lid of the recorder Clear view of the metal tape inside the cassette Overview of the various components

 
Further information

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Copyright 2009-2013, Paul Reuvers & Marc Simons. Last changed: Monday, 22 February 2010 - 13:12 CET
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