Sentry Mk2 Noise Controller Cut-off Type Excluding ContactorThe Sentry MK2 works in conjunction with a relay or contactor and usually controls mains power. It has been designed to solve some of the environmental noise problems encountered in entertainment venues and working areas. The Sentry MK2 Cut Off Limiter is designed to monitor sound levels and provide a trigger when a preset sound level is exceeded. The trigger will normally be used to trip a contactor removing the mains power supply to the music