Standby energy supply unit for signalling lamp

The supply unit has switches (F1, Fn) arranged in a driver card (22) for temporarily switching a main source (20) for signaling lamps (LED1, LEDn). The signaling lamps signalize risk by transmitting light. An auxiliary source (24) i.e. alternating current (AC) source, delivers AC voltage during failure of the main source. The auxiliary source is inductively coupled at an electric circuit of the signaling lamps to be supplied with energy via a transformer so that all signaling lamps are supplied with energy.