power supply and thus to a united whole, functional device, such as a nature - leak detection device.

摘要

When an AC mains powered electrical installation (5) having an earthed electrode (9) is provided with fault-responsive apparatus (6) powered by a circuit (10) which is also connected to the mains (3), it is desirable that the apparatus (6) should be arranged to perform its intended function even if the fault develops in the mains supply. For this purpose it is known for the power circuit (10) to comprise a rectifier circuit (22), first and second terminals (11, 12) for connection to the phase and neutral lines (7, 8) of the mains supply (3), and also a third terminal (13) for connection to the earth electrode (9) so that in the event of a break (20) in the neutral line (8) the power circuit (10) remains energised via the earth electrode (9) and the third terminal (13). In the invention, the power circuit (10) is made safer by providing a second rectifier circuit (24) between the third terminal (13) and the first rectifier circuit (22). IMAGE