Model: E18-D50NK
This is a set of transmitter and receiver in one of the photoelectric sensors. 1 detection distance can be adjusted according to the requirements. 
The sensor has a detection distance, by small visible light interference, cheap, easy to assemble, easy to use features,
can be widely used in robot obstacle avoidance, line piecework and many other occasions.

Electrical characteristics:     
U: 5VDC