TRX-20-35B Telephone Recording Jack (3.5mm) TRX20 These WILL NOT WORK with CORDLESS PHONES. The TRX-20-35B Telephone Record Unit (specifically for 3.5mm mic inputs) adapts a recorder to both single or multi-line telephones. Simple and easy to use, this unit connects quickly between your telephone and handset providing crystal clear audio recordings. (The audio quality will be as good as the audio coming through your handset!).A modular connector simply plugs between handset cord and the telephone, and 3.5mm jack plugs into your recorder.When used with a multi-line phone, it will record whichever line you are talking on.3.5mm microphone input plug on the tape recorder or digital recorder.