Sending Morse on a rig without a sidetone is not impossible, but is not particularly pleasant either. This battery-powered monitor has been designed to provide an audible indication of keying for those whose rigs lack a CW sidetone. Its sensor wire is wrapped around the transceivers coax no direct connection is required. Of course Morse isnt the only use for this nifty circuit it should also be useful any time you need a simple alarm that detects the presence of RF. RF collected at the sensor wire is rectified by a germanium diode. This produced a DC voltage that triggers a transistor switch.