Wired Security Alarm System Working Principle and Common Connection Method

Security is mainly divided into three major monitoring, alarm, access control. In the security group, we shared a lot of things about video surveillance, so we have to warn you today. Our common security alarm system is mainly divided into wired and wireless. Most of the home use is wireless, because it is easy to install, there is no cable restraint, and it does not destroy the overall home environment style, so it is deeply loved by home users. Smart home security products are mainly based on wireless alarms and monitoring.

However, in the business environment, or wireless systems in the disadvantages of the system engineering emerged. Therefore, the wired burglar alarm is stable and affordable, so it is trusted by most engineering companies. However, for those who are not professional, it seems that it is difficult to connect wired detectors and burglar alarm hosts. This reminds me of the scenario when using the DS7400XI for the first time. It is also a specification, a resistor, and a relay.

We know that the main components of an anti-theft alarm system are composed of three parts: the alarm main board, the front-end detector and the alarm sending device (network alarm communication and live sound and light alarm).

The front-end detector includes passive infrared, infrared plus microwave dual-mode, infrared radiation, infrared guardrail, manual alarm, fire house detection, glass breakage, etc., and is suitable for different environments according to different functions.

The front-end detector is the sensor of the alarm system. The detection of the outside alarm by the alarm system is accomplished through the front-end detector. The connection and signal transmission between the front-end detector and the alarm host are, in the final analysis, the transmission and reception of a digital signal. The so-called switching signal is an open circuit and short circuit of an electrical circuit.

Take the normal alarm system normally used as the normal closed working mode as an example. When the system is powered up and working normally, if the detector is de-energized or triggered by alarm, the relay in the detector sends out an action to change the contact from the closed state to the open state. When the alarm host detects this change of the corresponding zone port, it will take corresponding responses (including ignore, alarm, signal output, etc.) according to the current state settings.

In fact, the working principle of the alarm host and alarm detector is very simple, but why there are a lot of people can not be correctly configured and used in practice, in fact, some key basic knowledge is not how to understand it. Today we talked with you about the wired zone and the connection between the cable detector and the alarm system.

Basic knowledge can not be less: what is the end of line resistance.

End of line resistance (or end of line resistance) English EOL Resistor: End of Line (EOL, End of Line) circuit, the circuit is characterized by the loop terminal access resistor, circuit ground short circuit will trigger the circuit contact action, such as when the system is armed, A circuit disconnection or short circuit triggers an alarm. The scientific name for the wire tail resistance, the specific specifications of the line resistance at the end of the different brand models have their own specifications, each manufacturer's resistance is not the same, commonly used 1KΩ, 2.2KΩ, 4.7KΩ, 5.6KΩ, 6.8KΩ, security On various detectors, that is the end of the line.

Normally-closed quantities are connected in series in the circuit, and the normally-open quantity is connected in parallel in the circuit. When the alarm occurs, the host computer will detect the change of the resistance value. In other words, as long as the resistance output from the detector to the host is not the nominal resistance value. (Such as 4.7KΩ), it will alarm. The mission is to prevent vandalism. You can also call the police if you cut the line or short circuit. It is very clear that there are two ways of end-of-line resistance: one in series and one in parallel.

Common connection methods in the alarm host:

Normally Closed Loop (NC): Normal short circuit, open circuit alarm. The disadvantage of this circuit formation is that if someone shorts the line, the probe will lose its effect. The alarm host cannot recognize that it is a man-made short circuit.

Normally open circuit (NO): Short-circuit alarm, open circuit is normal. The disadvantage of this circuit formation is that if someone disconnects the line (shears the signal line), the probe is disabled. The alarm host will not be able to identify the segmented road.

End of line resistance EOL: short circuit is normal, open circuit alarm. The advantage of this circuit formation is that if someone breaks the loop (short-circuit return circuit), the alarm host can alarm. Short circuit alarm, open circuit fault, resistance (eg 4.7KΩ) is normal. The advantage of this type of circuit is that it reacts differently to short circuits and open circuits, especially for smoke detectors and emergency buttons. If a mouse bites a segment or is torn off due to help, the control panel assumes that the circuit is faulty.

Therefore, in practical applications, it is not only the detection of the end of line resistance but simply the connection of the normally closed and normally open circuits, which has a great potential for alarm safety.

The meaning of the alarm host AUX, Z-, Z+:

Unlike wireless detectors that use battery power, wired detectors typically use a DC voltage supply, and the AUX alarm host provides power to the cable detectors for the detector's power output. Normally, the voltage output from the alarm host AUX is DC12V and DC14V.

Z- represents the negative side of the wired zone, generally Z-ground (GND), Z+ represents the positive side of the wired zone, usually with a certain voltage.

Common connection for alarm detectors:

The front-end detector's lead port is generally six: power + (usually marked +), power - (usually marked as -), alarm normally closed output (usually marked as NC or ALARM), alarm signal common (usually marked For C or ALARM) and two split signal output ports (generally labeled T or TAMPER), we can achieve different tamper functions and alarm effects through different line wiring and resistance matching.

1, no tamper wiring

The tamper function of the detector is not enabled, and the alarm system cannot detect whether the detector is damaged. In this way, the alarm host does not have a separate tamper zone or tamper-proof setting. The detector signal wire only needs four cores. The wiring is the simplest and most reliable, but its safety is poor. In this connection mode, the alarm host can only detect if the detector is triggered by the alarm, but cannot detect other things such as the lid being opened and the line being destroyed (when the line is shorted, the alarm system still considers the detector to be working properly, and If the line is cut off or the detector loses power, the alarm system assumes that the alarm occurred.

2, separate tamper zone wiring

The detector tamper port signal is exclusively connected to the tamper-proof zone dedicated to the control panel. The wiring of this method is reliable and simple. The tamper-proof zone is individually programmed by the alarm host to achieve equipment and line detachment. Because additional lines are needed to deliver the tamper signal, the probe must be selected for more than six wires. In this wiring mode, when the detector box cover is opened, the line is cut or the detector loses power, regardless of whether the alarm system is in the armed state, the corresponding tamper-proof zone of the alarm host will be triggered to send the device to be disassembled and alarmed. However, this method does not trigger an alarm when the detector tamper interface or circuit is short-circuited, which has certain limitations.

3, single wire resistance wiring

This wiring method has the basic device tamper identification, and does not need to set up a separate tamper zone in the alarm host. The signal wire of the detector only needs four cores. It only needs to set the corresponding zone of the detector to the end of single wire. Zone. In this connection mode, the alarm host determines the alarm condition of the alarm condition by measuring the different resistance values ​​of the detector signal lines in different states.

4, double wire resistance

This wiring method has the strongest equipment tamper identification, and does not need to set up a separate tamper zone in the alarm host. The signal wire of the detector only needs four cores. It only needs to set the corresponding zone of the detector to dual. Line resistance zone. In this connection mode, the alarm host determines the alarm condition of the alarm condition by measuring the different resistance values ​​of the detector signal lines in different states.