Uploaded March 2021 | Updated September 2026, 2 weeks ago

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A look at an early key telephone system, and the modern homebrew key service unit that drives this one.

Relevant links:
seriss.com/1a2-ksu
seriss.com/people/erco/1a2

Greg Ercolano's YouTube channel, where he's posted a few videos of the 1A2 KSU and how it has evolved over time:
youtube.com/channel/UCxHid9oBBg5lJ4TL2fu0Y7g

A video of an original Western Electric 1A2 KSU working:
youtube.com/watch?v=-7AMBA4-PbA