Check the listing for details. 2x Ultrasonic Module HC-SR04 Distance 2pcs Detector Sensor Transducer b16. Condition: New. Listed at 10.44 USD. 2 Pieces - Ultrasonic Module. Test distance =. Input trigger signal: 10us TTL impulse. of this module is used as a switching output when anti-theft module, and without the feet when. Note : the module should be inserted in the circuit before been power, which avoid producing.