Ultrasonic sensor moudle Low cost, small size, switching signal output For alarm system, proximity switch etc. . Ultrasonic sensor1.TU-001 Ultrasonic ... directly, or connected to a alarm system to active a alarm or action also.2. Applications Alarm system, proximity switch etc.3 ... relay, buzzer directly, or connected to a alarm system to active a alarm or action also. special mini ultrasonic sensor, ...