RTS PS-20 power supply 

The RTS PS-20 is a complete independent TW (Two-Wire) power supply. The PS-20 features 2- and 4-channel operation, RTS monitoring, 2-channel program input, audio linking, and 3-mode operation: RTS 2-channel, RTS 4-channel and Clear-Com mode. It also has double the power output of the PS-31 per channel, this increases the number of user stations and beltpacks which can be connected substantially.