Abstract: A method for monitoring an entrance to a hazardous area comprising sensing a signal pattern generated by light barriers when an object passes the entrance and comparing the sensed signed pattern with at least one predetermined signal pattern. The object is admissible if the signal patterns are identical and under certain other conditions.

Abstract: An interface for light barrier arrangements operates with an optoelectronic data exchange that can be activated by means of a magnetically acutated switch.

Abstract: A circuit arrangement for testing of a tristate detection circuit has controllable switches (3-6) which simulate the three states: logical “1”, logical “0”, and high-impedance on a terminal (K1). Inputs (P1, P2) from comparators (1, 2) of the detection circuit are set to supply voltage or to ground. Switching of the comparators (1, 2) on and off is checked independently of the state on the terminal (K1).

Abstract: An interface for light barrier arrangements operates with an optoelectronic data exchange that can be activated by means of a magnetically acutated switch.

Abstract: A photoelectric barrier and operation thereof, the barrier having at least two pairs of transmitters/receivers each operating synchronously. Each of the two transmitters transmits a light signal having a specific identifier, the signal being in the form of a double pulse separated by a pause, which double pulse consists of two pulse groups each separated by a pause, and each receiver then evaluates a light signal of the associated transmitter as correctly received when at least one of the two pulse groups is recognized as valid by means of the associated identifier, in which the duration of the pulse groups and the pauses between them are established so that at most one pulse group of one double pulse of the one transmitter is superimposed with one pulse group of one double pulse of the other transmitter.