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PTT
Staatsbedrijf der Posterijen, Telegrafie en Telefonie

Between 1928 and 1989, Staatsbedrijf der Posterijen, Telegrafie en Telefonie (PTT) was the Dutch state-owned telecom monopolist, responsible for mail, telegraph and telephone services. It was the successor to the P&T, and was part of the Ministry of Transport (Dutch: Ministerie van Verkeer en Waterstaat). In 1989 privatised and split into Postbank (bank), TPG (mail) and KPN (telecom).


In the period following WWII, the Dr. Neher Lab of the PTT developed a series of cipher machines at the request of the Dutch Government. The production of these machines was later taken over by Philips Usfa. Until 1989, the Radio Monitoring Service (RCD) of the PTT was responsible for enforcement of the telecom laws, in particular with respect to the use of the radio spectrum.

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PTT cipher machines on this website
PTT Colex (predecessor of Ecolex)
EROLET, developed by PTT, manufactured by Philips Usfa
Ecolex I, developed by PTT, manufactured by Philips Usfa
Ecolex I Mark 2, developed by PTT, never produced in quantity
Ecolex II, developed by PTT, manufactured by Philips Usfa
Ecolex III (or Ecolex IIB), the synchronised variant of the Ecolex II
Machine development
The diagram below roughly shows where and when development and production of the various machines took place. Until 1957, the machines were developed by PTT but were produced, apart from the prototypes, at Philips Usfa. In 1957, the development was also taken over by Philips.


The first machines were developed immediately after WWII at the Dr. Neher Laboratory of the Dutch PTT by a team under Dr.Ir. R.M.M. Oberman. The first machine to be released was Colex, followed by Ecolex I and Ecolex II. The Ecolex III was never released, as development had mean­while been handed over by Philips Usfa. This resulted in Ecolex IV and further cipher machines.

Until 1960, all machines were One-Time Tape (OTT) cipher machines or mixers. When correctly implemented and used, such machines are unbrekable. Ecolex IV was the last OTT machine developed in the Netherlands. It was succeeded by Tarolex and later by Ecolex X, which were both cipher machines with a built-in key generator based on shift-registers.


Further information
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Crypto Museum. Created: Tuesday 08 December 2020. Last changed: Saturday, 19 August 2023 - 05:47 CET.
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