The SAR 4 and SAR 5 switches an external signal generator (e.g. bell, horn or lamp) through a contact with its own or separate power supply when a control voltage is applied (e.g. incoming call voltage of a telecommunications connection line). With the in-built switch the external signalling can be switched on or off. The SAR 4 and 5 are connected to a telecommunications line or to a direct-voltage signal source and controlled by the call voltage or the control voltage. The mounting is done on a carry rail TH35. With the help of two potentometers the call-pause bridging and the switch-on duration restriction can be set individually. This makes it possible to connect different devices like blinking lights or surge current switch. The SAR 4 and SAR 5 have a changeover contact for connecting the devices. Reaction only to the control voltage, not to the dial pulse (IWV).