Light barriers are contact-free protective devices to guard access to danger zones, dangerous positions and entry points. They are the optimum solution in most cases, especially when safety has to be assured without adversely affecting productivity or causing a hindrance.

Each interruption of a light beam triggers a signal for reliable interruption of a dangerous movement of a machine, plant or other motorized installation.

A complete system comprises at least one one-way light barrier with a separate emitter and receiver. Two different systems are available that are approved by an employer's liability insurance association as a unit for Safety Category 2 or 4 in accordance with EN 954-1:

• Category 2 with separate evaluation unit
• Category 4, operation without an evaluation unit is possible.

The 3RG78 23 light barrier (Category 2) only operates in combination with the 3RG78 25 or 3RG78 47 evaluation unit as a contact-free protective device. The 3RG78 24 light barrier (Category 4) can also be operated in combination with 3RG78 47 evaluation units.