Terminal Block for 34921A and L4421A Multiplexer. 34921T is a terminal block for the 34921A 40-channel multiplexer and the L4421A 40-Channel LXI armature multiplexer. It offers a built-in thermocouple reference junction that helps minimize errors due to thermal offset when you measure thermocouples. This terminal block is used for discrete wiring. It supports up to 20 AWG wire size typical for <100 connections or 24 AWG for >100 connections. The 34921T is a detachable terminal block with screw-type connections that provides a flexible method for connecting external wiring.