Anyone know what this is for?: AT&T ext SCSI drive

From: John Ruschmeyer <>
Date: Sun Dec 13 00:03:01 1998

> I found this while digging through a surplus store. AT&T external SCSI
> drive model DM/300S. It's a white metal box about 11" square and 4" high.
> Does anyone know what machine/system it's for or the specs for it? It has
> two round co-axial connectors on the back marked "Power" and "Control".
> Anyone know what they're for? It has a socket for an AC power cord so the
> "Power" connection isn't for powering the drive.

Sounds suspiciously like it's for a 3B2.

The 3B2 used an interesting daisy-chained soft-power scheme. When the main
system was powered up, it would put out 5V on a coax port on the back. The
5v would close a relay on the power supply of the expansion box (in lieu
of a switch) and turn on power to the expansion box.

I'm guessing here, but I assume that one of the ports is the 5v in and the
other would output 54v to power up the next peripheral in line.

Received on Sun Dec 13 1998 - 00:03:01 GMT

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