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Synchronizer - not in collection

BID/700, also known by its codename VENDOR, was a synchronizing unit, or synchronizer, for the BID/610 (ALVIS) cipher machine. It was developed by Plessey Crypto in Liverpool (UK) and allowed ALVIS to be used in mode B (synchronous operation). It also added Traffic Flow Security, or TFS.

Due to the way the Non-Linear Feedback Shift Registers (NLFSRs) inside the crypto logic of the BID/610 work, any transmission errors would propagate through the system, resulting in a garbled output. It then took a certain number of characters before it was synchronized again.

When the synchronizer was added, it produced a continuous timing, in order to keep the receiver in sync with the distant transmitter, even if the signal was distored or completely lost for some time. The synchronizer was typically used on low-quality HF radio links and bad phone lines.

The image on the right shows a complete BID-610 system with occupies a full-height 19" rack. The Large unit at the top is the BID/700 unit [2]. It is covered by a metal front panel for TEMPEST reasons, and has an oval window through which its indicator lamps are visible. The system shown here was used on a full-duplex HF radio link.

 More about BID/610 (ALVIS)
Photograph by Henrik Teller [2], obtained via Jerry Proc [1].

Foreign Office
The image on the right shows part of an array of BID/610 systems that were in use at the Foreign Office in Canada, probably during the 1960s or 70s [4]. Only the first two racks have a BID/700 mounted at the top. It is believed that only these two units were used in MODE B (synchronised).

The cover of the fist BID/700 has been removed, giving us a glimpse of the complex electronics inside.
Click to see more

BID/700 modifications
  1. All-space-deleter added for T.A.R.E. operation
  2. Improved crypto security
  3. Conversion to standard low-level logic 6V-0V-6V
  4. Elimination of security hazard (not low-level version)
  5. Switch added for 7 or 7½ unit operation
  6. Prevention of garbled receive copy
  1. Technical notes on BID/610, BID/700 and BAM/650, Part 1
    Part of technical training course in 1975.
    Secret/Confidential notebook 1 . CM-301917-C [3].

  2. Technical notes on BID/610, BID/700 and BAM/650, Part 2
    Part of technical training course in 1975.
    Secret/Confidential notebook 1 . CM-301918-C [3].

  3. BID/701/12A, Technical Description
    Not in collection.

  4. BID/701/12B, Fault Finding and Repair Data
    Not in collection.

  5. BID/701/13, Unit and Field Repair
    Not in collection.

  6. BID/701/14, Base repairs
    Not in collection.

  7. BID/701/37(1), Modifications
    Not in collection.

  8. BID/701/20(2), Illustrated spare parts list
    Not in collection.
  1. Declared unclassified by the author in 1993.

  1. Jerry Proc and contributors, BID/700 (Vendor)
    Retrieved May 2016.

  2. Henrik Teller, Image of rackmount BID/610 and BID/700
    Photographed at the Signals Regiment Historical Collection, Fredericia (Denmark).
    Retrieved May 2016 via [1]. Reproduced here by kind permission.

  3. Anonymous contributor, Technical training notes on BID/610 and BID/700
    Declassified in 1993. Obtained March 2014.

  4. Old Foreign Affairs Retired Technicians, Photograph of BID/610 units in Canada
    Website. Retrieved May 2016 from Ray Fortin, via [1].
Further information
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Crypto Museum. Created: Monday 30 May 2016. Last changed: Wednesday, 16 January 2019 - 22:56 CET.
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