| 摘要 |
To secure a door giving access to a room a magnetic latch is provided consisting of a electromagnet with which an armature fixed to the door engages. A magnetic sensor, e.g. A Hall sensor, monitors the gap field strength to indicate to a control circuit whether the door is open or closed. A second device consisting of a transponder on the door and an hf coil on the door frame provides a back-up system to check, based on the response received, whether the door is open or closed. |
