Beam sensors are intended to cover long hallways or perimeter areas. A
beam sensor consists of a transmitter and a receiver. The transmitter is
mounted at one end of a hallway and the receiver is mounted at the other.
The transmitter shines and invisible light at the receiver. If that light is
blocked from the receiver by someone walking in front of it, the receiver trips
As with most sensors, there are different designs for different applications.
Sensors come in different ranges for instance. You don't need a weather
proof sensor that can cover a 500 ft wide storage yard if you are only
covering a 20 foot long interior hallway. There are single and dual element
sensors. A single element sensor is fine for an interior hallway but in a
storage yard a bird flying thought the sensor could set it off. The dual
element sensor requires that both beams be blocked at the same time to
The biggest restriction with a beam type detector is that it must have an open
path between the two components. If you are using it on a storage yard for
instance and someone parks a lift truck in the path of the beam, it can't work.
Otherwise, they are a good choice for covering large areas or narrow
SEM Security Systems
a division of Southeast Mobility