It not only represents transmitted radio signals but also provides information about the quality of radio communication and the transmitter supply voltage. The red LED indicates, depending on the configuration of the radio receiver, either the status of the receiver supply voltage or the input of the receiver confirmation. An integrated buzzer also acoustically signals a confirmation from the receiver. If the confirmation is disabled, any change in the button state is reported instead. With the profile seal and a special keypad foil, the handheld transmitter is well protected against mechanical impacts and moisture, allowing it to be used in harsh and humid environments. The handheld transmitters of the SH-12 radio series operate with extremely low interference due to their special transmission characteristics. With interference-resistant radio transmission and extremely short reaction times, ranges of over 1000 m can be achieved. For strong narrowband interference or the use of multiple parallel radio systems, the operating frequency can be adjusted to individual needs. The SH-12 radio series can be operated in both unidirectional and bidirectional modes. In bidirectional communication, the transmitter automatically adjusts its transmission behavior to the quality of the radio link. The transmitters are factory-programmed with a continuous serial number, providing enhanced security and making each transmitter a uniquely distinguishable piece.