Keithley differential multiplexer plug in module 770x series keithley 7700 the keithley 7700 is a 20 channel differential multiplexer plug in module that offers 20 channels of 2 pole or 10 channels of 4 pole multiplexer switching that can be configured as two independent banks of multiplexers there are two additional protected channels for current measurements automatic cjc is provided so that no other accessories are required to make thermocouple temperature measurements in addition th