The switch shall be an external mute switch for connection to a PT 4000 or PT 450. The mute switch shall provide a locking on/off switch and a clip for fastening the device, e.g., on clothes. The RMS 4000 shall enable the user to mute a PT 4000 or PT 450 transmitter discreetly if the transmitter is difficult to reach when it is mounted, e.g., on the user's body. The switch shall be fitted with a 110-cm cable and weigh approx. 30 g.