| 摘要 |
A control device 24 is in the projection booth of a cinema auditorium, an electromechanical lock 23 is mounted above an exit door 17. The auditorium includes a main electrical circuit and a safety electrical circuit 7c, 7d with a DC current powering the emergency lights 15, luminous exit indicator panels, etc. The lock is mounted in a luminous exit indicator panel 16 and it is connected up in series with two diodes 29 on a bypass 27 between the terminals of the lamp 14 of the panel. The control device 24 comprises an inverter 32 changing the polarity of the lines 7c, 7d. This has no effect on the lamps 14, 15 which operate in both cases, but makes it possible to lock or unlock the door 17, the diodes 29 allowing conduction in just one direction. Use for avoiding having to resort to a special line. <IMAGE>
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