[Boatanchors] Relay Contacts, etc.

[Jim Haynes]

On Tue, 2 Feb 2010, mac wrote:

> The old (40s/50s) IBM tabulating systems used hundreds of wire contact
> relays and the circuitry was specifically designed so that the
> contacts NEVER made or broke current.  Timing was such that all relay
> contacts were either open or closed before current pulses were sent
> through the logic.  These relays used removable wire contacts on the
> armatures and special burnishing and other tools were provided for
> their maintenance.  Does anyone remember the maintenance protocols for
> these components/equipments?
>
> Dennis D. W7QHO
> Glendale, CA

I don't know anything about the protocols, but I remember on first seeing
one of those relays how amazed and delighted I was with the design.
IBM had, in addition to a formidable sales force, some manufacturing
engineers who were outstanding and designing things so they could be
manufactured inexpensively while maintaining excellent quality.

The fixed contacts were an integral part of the plug-in base.  The
moving contacts were twin wires for reliability; and could be replaced
by just pulling them out and pushing new ones in.

IBM did have another line of relays, similer to the "telephone type",
for use in power controls and other applications where it was necessary
for the contacts to make and break current.