On 31 Aug 2007 ethan wrote:
Fairchild Panel Meter> Model Number 300555>
5VDC
Powered: 2V F.S. Range> 7825 (in paint, presumably a date code)
I found mention of a Fairchild model 300550 DPM in a 1982 US patent,
so your 1978 timeline would seem to be about right. Said patent has
a schematic that includes the panel meter, but the pinouts given seem
to be for a standard 14-pin DIP socket, so no luck there.
All the schematic would tell you are the signals required for the DPM
operation. I can dig it up again in the USPTO database if you're
interested.
Cheers,
Chuck