This is a NEW Peripheral Electronics (now PAC Audio HFS) MSS relay. This is used to integrate a handsfree phone kit (like the Motorola IHF1000 bluetooth carkit) into the vehicle audio system. When the handsfree system is active, the radio audio is muted and the handsfree kit audio is routed to the front speakers. This speaker switcher is used in conjunction with a vehicle-specific handsfree harness (some of these harnesses are also available in my booth). This switch is now called the PAC Audio HFS. It also includes a P-M2UP phone interface harness for direct connection to Motorola IHF1000, IHF1700, T605 and T603 carkits. It can be adapted to work with other handsfree carkits as well. I have a mobile electronics installation business, and am selling off some excess inventory. Please feel free to send a message if you have further questions about any of my items. Thanks for looking!