[GreenKeys] Can you identify the equipment in this picture?

[Jim Haynes]

On Wed, 24 Feb 2010, Tom Dawson wrote:

> So what are the equipment with "tuning" forks?
>
Well, y'see back then they were running time division multiplex with
mechanical distributors, so that requires running motors exactly in
phase at both ends of the circuit.  And you couldn't rely on the
frequency of commercial power back in those days.  So the tuning forks
are frequency standards for controlling the distributor motors.
This was pretty high-technology for its day.

If you really want to get into it there are some articles in Western
Union Technical Review, which is online, just google for it.