PLUTO for registration of intercepted radio-telex messages (1966)
In 1966, the interception department of the Royal Air Force (45 LUVE) at Camp Blikkenburg, Zeist had also the need for a registration system for intercepted military radio telex messages from behind the former Iron Curtain. Therefore, TNO Waalsdorp developed PLUTO (Physical Laboratory Universal Telegraphs Receiving System), a device for the interception of mostly encrypted military telex messages. The device had a bit synchronisation system to extract the telex code from the intercepted radio link, of which the baud rate was unknown beforehand. The bit synchronisation had to be set very accurately in order to be able to bridge long signal interruptions due to fading. PLUTO contained the functions of the earlier PUNCHROPHYL and the SCRIBOPHYL.
A time clock was also made, which regularly supplied a modulated time signal to the many recording recorders linked to the RACAL radios. That timestamp was included in all messages registered by PLUTO, both in the directly punched paper tape and on the with recorders registered messages. On the right side of the printout, the clock time was printed so that the clock time of the message’s passage was also next to the registered time. The time clock was the first TNO-developed device based on wire-wrapped integrated circuits (TTL) from the SN7400 series. The time signal was fed in some modulated fashion to the many recorders. The registration recorders recorded the messages that were later processed using PLUTO’s decoder and control electronics and printed on an IBM model 73 typewriter. In addition, fault and time indications were recorded in the paper tape.