A15TG tone generator is a battery-powered 700Hz signal source that can be used to troubleshoot low-impedance, balanced-line microphone inputs. It includes a recessed On-Off switch and a three-pin XLR audio connector. A removable end cap allows easy battery installation and removal. It can also tolerate the presence of phantom power, or a short circuit in the line it is driving. Built-in short circuit protection allows normal operation to resume after a short is removed.