The TP-7 is a supersensitive microphone for telephone conferencing. Just plug it into the "MIC" jack of your recorder, and put the earphone side into your ear. When speaking on the telephone, the TP-7 will capture both sides of the conversation for recording on your voice recorder. Frequency is 50 - 20,000 Hz. It plugs into a 3.5 mm monaural jack and comes with 2 plug adapters to convert either to 3.5 mm stereo plug or to a 2.5 mm monaural plug.