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Ecolex IV →
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Ecolex III
One-time tape cipher machine - this page is a stub

Ecolex-III was a One-Time Tape (OTT) cipher machine (mixer), developed by Philips Usfa around 1959, as the successor to the Ecolex II. Contrary to the Ecolex II, the Ecolex III featured advanced synchronisation for use over noisy narrowband Short Wave (HF) radio channels. The machine was known by NATO as Ecolex-IIB and eventually evolved into the extremely successful Ecolex-IV.

The machine clearly follows the design strategy of the earlier Ecolex II and it based on a existing Siemens twin tape reader, identical to the one that was used for the Ecolex II. It is mounted on top of the actual mixer, which has become much larger due to the fact that is now includes a complete synchronizer as well. This is illustrated by the two prominently visible counters (DELAY and ADV) at the front panel of the bottom unit.

The image on the right shows a prototype of the Ecolex III , but it is uncertain whether it was ever taken into production, as no production records of it have been found to date. It is not listed in the internal Philips memo [2], which is otherwise known to be both accurate and exhaustive.

On the other hand, the machine was tested and approved by SECAN, NATO's certification body, on 19 November 1959 [3], which means that at least a fully operational prototype must have existed and that all SECAN recommendations had been followed and implemented. In the approval memo [3] NATO even refers to this.
Ecolex III (or Ecolex II B) which was approved by NATO but was probably never taken into production.

The image above also shows a line interface (or actually a filter) at the right. This filter is identical to the one that was later supplied with the Ecolex IV. As we were unable to find any records referring to the Ecolex III or the Ecolex II B (apart from the NATO approval), we assume that the machine was never taken into production and that it was later re-released, probably with some improvements, as the Ecolex IV which supports both synchronised and non-synchronised traffic.

  1. Photographs from Philips Usfa
    Crypto Museum Archive.

  2. Philips Usfa, Internal Memo L/5636/AvdP/JG
    23 August 1982, page 5.

    SGM-660-59. 19 November 1959. NATO SECRET.
    Declassified by NATO on 5 January 2000 (IMSM-431-99).
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Crypto Museum. Created: Monday 25 May 2015. Last changed: Monday, 11 January 2021 - 20:15 CET.
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