Monoprice 108134 Tone Generator with Probe Kit The Monoprice Pro LAN Tracer/Toner is a professional tool used to test and troubleshoot RJ11 cables and individual wires The tester is composed of two individual units: the Tone Generator and the Amplifier Probe Each unit is constructed of plastic and is powered by a 9 volt battery Two 9 volt alkaline batteries are included in the packaging