The RDL ST-SX4 is a four-input, single-output audio switcher in RDL's "Stick-On" line of products. It will send any one of the four unbalanced audio signals to the unbalanced output, or all of the sources may be switched off. A single input terminal provides control of the unit.
The desired input is switched on when connection of a specific resistance is made between the "Ctrl" input and the ground. The required resistors are included with the ST-SX4. The unit may be controlled by the RC4-ST remote control from RDL.