[GreenKeys] Ring generators

[John Nagle]

> I was curious, how did the telco COs generate their ring signal? I
> believe that it is a 20 Cycle AC current.

     The classic Western Electric ring generator was one of those
clever devices from the golden age of passive components.  They
used inductors and saturable reactors to create an oscillator
that ran off 48VDC with no tubes or moving parts.

     Western Electric liked non-linear magnetic devices.  They
don't wear out.  There's a whole forgotten technology in that
area.  In the 1940s through the 1960s, a whole range of devices
were developed, including magnetic amplifiers and magnetic logic.
There was even a magnetic logic computer, the UNIVAC Solid State 80
machine.

				John Nagle