RTS PS-15 power supply 

The PS-15 Power Supply is designed to work within the TW (Two-Wire) Intercom System. The PS-15 is suitable for small to medium sized TW Intercom Systems. The unit is self-contained and features 2-channel operation: one (1) wet channel with 24 to 32 volts DC and one (1) dry channel without voltage potential. Each channel provides an audio termination impedance of 200 or 400 Ω (switch selectable).