This Agilent / HP 44421A 20 Channel Relay Multiplexer is used, and in excellent condition. This is option 010 for the 3497A Control Unit. There are screw terminals external connections.
This assembly uses reed relays to multiplex signals to the DVM or other instruments. Each assembly switches 20 channels; each channel consists of Hi, Lo, and Guard lines. Two channels may be closed per assembly and relays may be closed in a random sequence or incremented between programmable limits. The low thermal offset of the relays make it suitable for measuring the outputs of strain gage and other transducers. Each channel can be configured with a filter of current shunt for additional flexibility.