The 77HP-G Tone Test Set is housed in a high impact plastic case and is powered by one 9 volt battery. Standard test leads include red and black rubber insulated test clips and a snag-proof 4-conductor modular cord and plug.

In addition to the test lead strain relief, the 77HP-G provides a durable lanyard for carrying or hanging the tester. A three-position toggle switch controls the modes of operation and two (2) bicolored Light Emitting Diodes (LEDs) display line polarity for Lines 1 and 2. The tone and continuity test functions are only applied to Line 1 using the modular plug. A tone selector switch located inside each unit, may be used to select a fast or slow warble tone output.

The 77HP-G is compatible with all common Central Office Switching Systems and the output tone is isolated from DC voltages.