| 摘要 |
A security device for protecting premises having three separate variable time delays. A first time delays allows a legitimate user of the device to enter the premises and de-activate the device before the alarm sounds. The second time delay permits a legitimate user to exit from the premises without sounding the alarm. The third time delay ensures that the alarm will sound for a minimum period once the loop has been opened by an intruder. The device has an integrated circuit and each of the time delays are achieved through the use of a resistor in combination with a capacitor. The device also has a supervisory loop and the alarm becomes activated when the loop has been opened.
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