Wirt Atmar wrote:

> As a side note, people have a tendency to vastly underrate relays as logic
> devices, but you could build an entire computer out of them, CPU, memory,
> everything. Clearly, it would be a little slow, awfully big, and very noisy,
> but it would work. Indeed, Shannon defined the logic of computers not around
> the circuits that we now use but only with these kinds of relays in mind.

I own an old IBM 360/65 front panel, complete with 4-byte registers of
lamps.  There are also 4*8 toggle switches so you can "enter" a value.
The old bugger has a parity bit per byte.  The switches are multi-throw
of some fashion (haven't torn one apart) but I did have it wired up to
a healthy 5-volt power supply so you could toggle the register lights
on and off with the switches.

The "underrated" part is that it computed parity on the bits and the
parity light would turn on or off automagically.

Jeff

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