The ST-RX2 has a single line-level audio input and two line-level audio outputs. In the absence of a control input, the NORMAL module output is fed from the audio input. When the TRIG control terminal is connected to ground, the input audio is fed to the SELECT output and the NORMAL output is switched off. When the TRIG terminal is again disconnected from ground, then the SELECT output is turned off and the NORMAL output is fed from the input. The module contains no relays or other mechanical devices.

The control circuits utilize solid-state switching to route the input signal to one of the balanced output line drivers with off attenuation better than 80 dB at all audio frequencies. Soft switching is used to eliminate clicks or pops.The control current required at the TRIG terminal is so minimal (< 0.5 mA) that the ST-RX2 can be controlled from nearly any source from switches to logic circuits. The ST-RX2 may be controlled using the RDL RC2-ST, RT2 or RUC-4 remote controls.