Abstract: A control method and apparatus for a door-locking mechanism which includes an electrically-released latch, to lock the door closed. A processing unit sources first and second data streams each of a repeating string of binary data, the two strings being of the same bit length and bit rate, the processing unit also having two sensing inputs. A normally-open first switch is associated with the latch and connects the first data stream to the first sensing input other than when the latch is released, and a normally-open second switch is associated with the door and serves to connect the second data stream to the second sensing input so long as the door remains closed. A normally-closed third switch is also associated with the door and serves to link together the first and second sensing inputs when the door is not closed. The processing unit outputs a signal indicative of an error condition should the data stream which appears at either sensing input not be the expected stream.

Abstract: A control method and apparatus for a door-locking mechanism which includes an electrically-released latch, to lock the door closed. A processing unit sources first and second data streams each of a repeating string of binary data, the two strings being of the same bit length and bit rate, the processing unit also having two sensing inputs. A normally-open first switch is associated with the latch and connects the first data stream to the first sensing input other than when the latch is released, and a normally-open second switch is associated with the door and serves to connect the second data stream to the second sensing input so long as the door remains closed. A normally-closed third switch is also associated with the door and serves to link together the first and second sensing inputs when the door is not closed. The processing unit outputs a signal indicative of an error condition should the data stream which appears at either sensing input not be the expected stream.