This Extech Wireless Transmitter allows remote viewing from up to 100 ft. away, allowing you to use your borescope in hard to reach areas while keeping the display at eye level. Probe in. 39. On board controls to adjust the brightness of the LEDs on the camera probe Works with Model#s HDV610 and HDV620 Northern Item#s 23640 and 23641 Uses the same battery and charger as the compatible borescopes Waterproof design Comfortable molded grip for one-hand operation.