IR Light Barrier

Includes transmitter (2.1" x 1.6") and receiver (3.9" x 2"). The kit transmits a light beam between the transmitter and receiver up to 4 meters. When the light beam is interrupted the kit makes an audible noise (85dB). The transmitter and receiver, both require a 9V battery (not included). Comes with battery holders and adapter jack. Kit comes with complete parts and instuctions.