Abstract: A compact, hand-held electrical line tester includes a normally-open relay switch which is closed by connection of its relay portion to a line of a predetermined voltage level, and a piezoelectric tone generator, connected in series with the relay switch and a battery, which emits an audible sound to indicate that the tested line is electrified with the predetermined voltage level. The tester circuit can include a plurality of relay switches and/or tone generators for emitting different sounds in response to different line voltages, so that the user can determine the line voltage(s) without having to check a light indicator or read a dial.