On Thu, 28 Feb 2002, Jim wrote:

> Specifically, they read the voltage pulse produced on
> the 'Z' wire which caused by the 'intersection' of the
> 1/2 currents on the X and Y wires during a magnetic
> core memory read cycle ...

Yes, in fact I still have some buffer core fom an old IBM 2821.  It's
4-wire, IIRC - X, Y, SENSE and INHIBIT, faster than 3-wire.  Sense amps
were also used in tape drives, but I don't remember whether there was any
common ground between core and tape as far as parts go.

Dale

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