When build for Standard UNIBUS, UniProbe is plugged into the backplane "end" sockets and must act as bus terminator. It is identical to a regular M9302 terminator card then.
With inline resistor packs we can build it smaller:
There are some differences to the original M9302:
- the voltage dividers are not 178 / 383 ohm, but 180 / 390 ... the ratio error is 1%.
- the source voltage for the terminators can be separated from +5V.
By varying the terminator voltage, "Margin Testing" on the bus can be performed, as described by DEC. - the M9302 terminator has "SACK turnaround logic."
This function answers any BUS GRANT with a proper SACK, if a GRANT is ignored by all device cards.
Here it can be disabled by a jumper, converting UniProbe back into an older M930 terminator.
