The Total Recall TSA-3PB is used to provide a simple and inexpensive method of coupling audio from an external source into your desk telephone. It can be used with most telephone styles that have a standard modular handset or headset jack. Connecting between your phone and the audio output of your computer sound card, audio recorder, radio, etc. The Total Recall TSA-3PB features: isolated and adjustable audio output; RF Bypass; and a three position function switch.