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The BID 770 was a British-built electronic cryptography device, codenamed TOPIC. It was also used by Canada's foreign service under the codename TENEC. TOPIC was brought into service in 1977, and became obsolete in 1995.
![](http://upload.wikimedia.org/wikipedia/commons/thumb/c/cb/TOPIC.jpg/320px-TOPIC.jpg)
TOPIC was used to protect telegraph traffic, and replaced the earlier mechanical system called ROCKEX. It could be operated in both on- and off-line modes. Weighing 65 lb, the machine used diode–transistor logic instead of single transistors.