Selectric Typewriter conversions

From: John Honniball <>
Date: Tue Feb 4 19:37:01 2003

Tony Duell wrote:
> I have a reprint of an old (1912-ish) book on Telegraphy, and it uses a
> similar linkage for a binart to 1-of-n decoder to position a typewheel
> for a printing telegraph machine. So the idea is pretty old.

I've seen a 3-bit-binary to one-of-eight decoder built out of
huge brass and bakelite relays. It's in the London Transport Museum,
and was used to drive the train indicators on the platforms of
the London Underground (subway). The train indicator tells the
passengers where the next train is going to by lighting up an
arrow next to the name of a station. Only three wires need be run
along the tunnels from the signalbox, giving seven possible
destinations and an "off" state.

John Honniball
Received on Tue Feb 04 2003 - 19:37:01 GMT

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