PAC OS-2C OnStar Radio Replacement Interface for Cadillac CTS/SRX with Chime Module Replaces factory radio in Cadillac CTS/SRX while retaining OnStar Plug & play-no cutting or splicing into factory plug Communicates directly with OnStar module to prevent false triggering & eliminating unwanted audio noise On-board amp will drive two 4-Watt speakers in stereo Use with existing factory speakers or external speakers