EOL wiring in Alarm Installation

Why would you require wiring detectors with end of line resistors? I have seen lots of domestic intruder alarm systems are being wired without an EOL resistor, some alarm installers do not see the advantage of wiring end of line resistors. Below are two circuits, open and closed. If the loop in the detectors is short-circuited, it will trigger the alarm and if it’s closed, it will not.

Therefore the result is either close or open.

 

 

 

 

 

 

 

 

 

 

There are chances that the wires short-circuited before they reach detector, this will not trigger the alarm as panel will still see it as closed. Therefore this is not a fully supervised loop.

 

By adding a resistor at the end of the line (in detector), panel can supervise the whole loop. For example if 2K resistor is fitted at the end of the circuit, when the circuit is completes at the panel, now the panel can read the precise resistance. It is important to fit the resistors inside the detectors and not in the panel.

 

 

 

 

 

 

 

 

 

 

 

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