Colex, the abbreviation of Code-Telex, was a One-Time Tape (OTT) cipher machine, also known as mixer. It was  developed in 1946 by Ir. Roelof Oberman at the Dr. Neher Laboratory in Leidschendam (Netherlands), at the time part of the Dutch state-owned telecom monopoly PTT. The device was developed at the request of the Dutch Government, who ,based on wartime experience, did not trust foreign cipher equipment, as it might contain weaknesses or even a deliberate backdoor.

For more information on the Colex, please visit the Crypto Museum web page.

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July 26/22