Auxiliary module for NMT-xxx transponders. The main function of the RSW2-A version is the 3 state (0 dB, -6 dB, -50 dB) switch in the return path, this is completed with an ingress measurement function. For the allowed ingress level a minor and a major limit can be set for sending minor and major alarms, while a third limit is set for controlling the switch - if the ingress level exceeds this limit, the switch goes into a predefined state. By switching off this function, the device can be used by the same way as the average ingress switches. The RSW2-H20 version contains a 4 state (0 dB, -6 dB, -50 dB, HPF) switch, it makes possible to switch on also a 20 MHz highpass filter. The use of this filter allows to get information on the ingress properties in the frequency range - without costly spectral analysis. Based on this the failure type can be evaluated.