The Bogen CA17 Call Switch is a momentary-push switch designed for use with PI/SI35A Intercom Systems in conjunction with the SCR25A. When pushed and released once, a signal is sent to the MCP35A via the SCR25A call-in module to annunciate the call-in on the SBA225.The room must be equipped with a 25-volt speaker. The CA17 is designed for flush-mounting in a standard single-gang outlet box. Also known as -Bogen Communcations CALL IN SWITCH SWITCH PUSHBTN - BO-CA17