Scan-Lock Siren Tones allow for user-selectable siren tones via momentary recessed switch. Operates up to two 100-watt speakers. "Hands-Free" operation. Turn On/Off and access all three siren tones (default Wail, Yelp and Piercer) without taking hands from steering wheel. Two manual functions allow for additional siren tone choices when you need it the most. PTT (push to talk) switch on microphone overrides all siren functions transfer switch.