Difference Between 2 Wire and 4 Wire Smoke Detector for Alarm System

Difference Between 2 Wire and 4 Wire Smoke Detector for Alarm System

Your home or business alarm system protects both from intrusion, but often uses smoke detectors to provide protection against fire.  For low voltage alarm system smoke detectors, there are two basic wiring types.  2 Wire Smoke Detectors and 4 Wire Smoke Detectors.  Both do the same job but they connect differently.

Alarm smoke detectors are powered devices - they use the alarm system power (and battery) as a power supply.

2 Wire smoke detectors use the same wire pair to provide both power to the detector as well as carrying the signal back in case smoke is detected.  The wires connect to the PGM terminals on your alarm system.

4 Wire Smoke Detectors 2 wires to provide power from the security system auxilliary output connections.  They use a second set of 2 wires to connect to a zone input on the security system.  2+2=4 hence the term 4 wire.  They offer the advantage that the panel knows which detector has been triggered in case of a fire (or false alarm).

We have a selection of 2 wire and 4 wire detectors for alarm systems here:

As an example, FSA-210AST or 528B would be 2 wire detectors and FSA-410AST or 541NB or 2012J would be 4 wire detectors.  We may show others on the site as well.

    • Related Articles

    • Wiring / Connecting 2 Wire and 4 Wire Smoke Detectors to an Alarm System

      We are often asked how to connect low voltage smoke detectors to a wired alarm system.  First we need to point out that smoke detectors are a life safety product and so it's critical that you read and understand how the connection should work, and ...
    • Add existing wired smoke detectors to a DSC alarm system

      We are often asked how to add existing smoke detectors to a DSC alarm system. There are 3 options we can suggest: Install DSC wireless smoke detectors separately so they don't interfere with your current system. This has the benefit of having each ...
    • Troubleshooting a Beeping or Chirping Smoke Detector or Carbon Monoxide Detector

      If your smoke detector or carbon monoxide detector is sounding an alarm, you need to take action immediately to check for smoke or in the case of a carbon monoxide alarm clear the building and call the fire department to check for dangerous CO ...
    • Connecting 2012JA 4 Wire Smoke Detector

      For liability and safety reasons we can't provide advice or direction related to your specific panel or installation, however we can provide some general guidance: Power Input will connect to the power output of the panel, possibly an aux out, that ...
    • What is the difference between the 2 Wire and 4 wire smoke detector

      2 wire smoke detectors connect with only 2 wires back to the panel, and can only be connected to the 'smoke zone' on the panel.  Their is typically one zone set aside for this on each brand. 4 wire smoke detectors use 2 wires for power, 2 wires for ...