| 摘要 |
The safety lock or bolt with progressive nature comprises a secondary circuit 10, a key and a primary circuit comprising a voltage source 21 connected to an alarm or self-defence device 23. The secondary circuit comprises a low-voltage DC voltage source 9, a selective switch 14 and two contacts 15, 16 respectively joined to the terminals of the voltage source of the secondary circuit, means 12 for linking the primary circuit with the secondary circuit being provided so that insertion followed by turning of an inappropriate key makes the electric contact between the two contacts and triggers the alarm or self-defence device 23. Detector heads m, n, o are mounted at the terminals of the said contacts in order form a monitoring station. <IMAGE>
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