The TX-TPSA1A module provides one Format-A input on the front panel. The input RJ45 connector accepts a twisted pair cable coming from one or multiple Format-A senders. This input receives and sums the signals received on the three pairs A, B and C. The summed output is fed to one of the OUTPUT pairs A, B or C selected during installation using the front-panel selector. The two remaining pairs are available for signals to pass through from other Format-A senders connected to the LOOP IN jack. Because this module drives only one pair of the output cable, the RJ45 LOOP IN jack can accept two signals and power from other Mic or Line input Format-A modules. Two single-pair senders can be connected to the LOOP IN jack, or one sender that uses two pairs.

The TX-TPSA1A may be powered from any of the RJ45 jacks, which provides power to the two remaining RJ45 jacks. The module may also be powered from an external 24 Vdc power supply connected to the DC input jack, which provides power to all three RJ45 jacks. Output voltage is protected by an automatically resetting fuse. A blue front-panel LED indicates the presence of valid power.