How Are Alarm Systems Wired
Common connection of alarm detector:
Front-end probe lead ports generally have six: power supply + (generally marked +), power supply - (generally marked -) normally closed, ALARM signal output (generally marked as NC or ALARM), ALARM signal common (general markers for the C or ALARM) and two open signal output (generally marked as T or TAMPER), we can achieve the effect of different TAMPER function and ALARM by the different circuit wiring adaptor, and resistance.
1. without tamper
If the detachable detector is not enabled, the alarm system cannot perceive whether the detector is damaged. The wire connection in this way is not set in a separate detachable defense zone or detachable defense setting in the alarm host, and the signal wire of the detector only needs four cores. Its connection mode is the most simple and reliable, but the security is poor. In this connection mode, the alarm host can only perceive whether the detector is triggered by an alarm, but cannot detect other cases such as the box cover is opened and the circuit is damaged (when the circuit is short-circuited, the alarm system still considers the detector to be working normally, while when the circuit is cut or the detector loses power, the alarm system considers the alarm to occur).
2. with tamper
The detachable detector port signal is specially connected to the detachable defense zone dedicated to the alarm host. The connection of this mode is reliable and simple. The detachable defense zone is separately programmed by the alarm host to achieve the detachable defense of equipment and circuit. Because additional lines are required to transmit anti-detachable signals, the detector wire must be selected with more than six cores. Under this kind of connection mode, when there is a detector, lifted the lid is opened or detector lose electric circuit was cut out, no matter whether alarm system in the protection state, corresponding tamper alarm host defence issue equipment be open alarm will be triggered, but this way the spacecraft tamper interface or line is short circuit when there will be no alarm is triggered, has certain limitations.
3. line resistance connection
This wiring mode has the basic anti-disassembly identification of equipment, and there is no need to set up a separate anti-disassembly and defense area in the alarm host. The signal wire of the detector only needs four cores, and the corresponding defense area of the detector only needs to be set as the single-line end defense area. In this connection mode, the alarm host determines what kind of alarm is happening by outputting different resistance values of detector signal line in different states.