The Shure A15TG Tone Generator is a battery-powered 700 Hz signal source used to troubleshoot audio systems by checking microphone lines for correct patching and detecting unusual noise that is present.The output level of the A15TG is approximately -42 dBV. This allows it to be used with either microphone level or line level inputs and the barrel design allows it to be connected to a microphone cable or directly to a mixer input.The A15TG can tolerate the presence of phantom power or a short circuit in the line that it is driving. Additional features of the A15TG include a recessed On-Off switch, a Male XLR output connector, and a removable end cap allowing for easy battery installation and removal. Battery life is 1,000 hours of continuous use.