285,622. Elwess, E. Jan. 7, 1927. Indicators, alarm and signal. - A device for indicating when the electrolyte in a battery falls below a predetermined level comprises a supplementary electrode 10 connected to an electrically operated indicator 2. The return lead 6 is connected to one of the battery electrodes 14 so that the power for operating the indicator is derived solely from the battery under test. The indicator consists of a lamp 3 and the circuit includes a switch 5. The electrode 10 may be made of soft metal so that it can be cut to any required length.