By including function blockings in the bay interlock conditions, switching operations can be prevented independent of the switching status at the time, for example, by an external signal “CB drive not ready” or by the trip command from an external protection device.

Binary input signals conditioned by debouncing and chatter suppression or output signals from the programmable logic function can be assigned to the function blockings 1 and 2 by setting a ‘1 out of n’ parameter. The input signal from the function blockings starts a timer stage and after it has elapsed, the signal MAIN: Fct. block. 1 active or MAIN: Fct. block. 2 active is issued.