[LeakyGrid]

In the late 1950s early 60s, working as a technical writer, I was involved in the conversion of the Type 85 radar from its missile guidance role to air traffic control.

Communication between controllers was handled by a new system supplied by Ericssons Telephones of Beeston, Nottingham. The relay units were fairly standard, but the audio units were solid state and used the then new OC71s etc. My memory of these units is a bit vague now, but I recall the use of emitter-followers with a common load to mix controller channels, and super-alpha pairs to increase input resistance.

The level of technology can be judged from the fact that the video for the target labels on the ppi displays was produced by video cameras scanning artwork of the characters.

Roger