Agilent Technologies 34921A User Manual page 14

34921A 40-Channel Armature Multiplexer with Low Thermal Offset
Low thermal offset voltage makes the 34921A ideal for low- level signal
switching. The 34921T optional terminal block provides a built- in
thermocouple reference junction that helps minimize errors due to thermal
offset when you measure thermocouples.
This module has capability to scan as many as 100 channels/second using
the internal DMM. With the automatic "break- before- make" connection
operation, you are assured that no two signals are connected to each other
during a scan. When using the module in a non- scanning mode, you can
close as many channels as you wish.
This module is safety interlock protected, which means whenever the
D- sub connector end of the modules is exposed, the Analog Bus relays
automatically open and disconnect from the Analog Bus. For more
information, see
Connectors"
When power is off, all channel relays maintain state, and the Analog Bus
relays open.
8
"Safety Interlock"
on page 10.
Agilent 34921A-34925A Low Frequency Multiplexer Modules User's Guide
on page 3 and "34921A D- Sub