While the boom gate has a built-in photoelectric cell, photoelectric cells are also useful on sites as individual components. They are essentially a switch that is tripped when a vehicle cuts the beam of the cell.

When installed at strategic locations, the photoelectric cells can alert operators or supervisors to the proximity of a vehicle on site. For example, a photoelectric cell can be installed at each end of a weighbridge. The cells can be integrated to a software package, supplied by QWM. If a vehicle is not fully on the weighbridge, one or both of the cells is tripped. The software can be programmed to fail to process this vehicle until it is fully on the weighbridge.

Photoelectric cells are economical site security accessories.

Transponder tags (devices that are uniquely encoded with an identification number, often with millions of possible numbers) can be issued to suitably authorized personnel. These personnel can then be individually identified by a semi-automated or fully automated system.

Personnel without a transponder tag, or those with one but with an identification number not accepted by the system, can be restricted from certain areas, or restricted from part or all of the system.

See Electronic Identification Systems for more details on the types of transponder tags available and their advantages and features. Shown below is an i-Button key tag (left) and a magnetic strip card reader (right).