Motor pump unit with sensor power supply using the mains connection

The unit has a pump (1) driven by an electric motor (2) supplied through a cable (5). The pump cut-off responds to signals on the supply line. A pulse train generator (37) couples pulses onto the supply line through a transformer (6,7) to supply the effluent level detector (21) through a second transformer (8,9). The level signal is returned when linked multiplexors (16,39) pause the pulse supply.