I recently picked up an HP 12979 I/O extender with some cards and now I'm looking for manuals. If someone has manuals for any of the following and could scan them when time permits that would be much appreciated. (Yes, I did check bitsavers before asking.) 12979A 12979B 12979C I/O Extender 11629-60001 44 BIT GPO (General Purpose Output?) I can't find any references to this card. Looks like it basically has a transister (or pair) for each output bit. 12551B Relay Output Register 12554A 16-Bit Duplex Register 12604B General Purpose Data Source Interface A Pocket Guide to Interfacing HP Computers (5950-8718) contains some information on these cards. 12661A Digital Voltage Source Programmer Apparently this would be used to control equipment such as the HP 6131B Digital Voltage Source.