Frequently Asked Questions

Supervision and the EOL Resistor

• 1 - Why Does the Fire Alarm Panel Supervise the Wires?

Signal and Power Flow

• 2 - What is a Fire Alarm Signal?
• 3 - What is the Difference Between Electricity Flow and Signal or Power Flow?
• 4 - How Are Fire Alarm Loops Supervised?
• 5 - Why is Supervised Wiring So Important?
• 6 - What is the End of Line Resistor For?
• 7 - What Makes the EOL Resistor so Important?
• 8 - The End of Line Resistor Pulls the Voltage Down?
• 9 - Why Use Pigtails or a UL Listed End-of-Line Resistor?
• 10 - Why Isn't an End of Line Resistor Used the Same Way as a Terminating Resistor?

Circuit Classification

• 11 - NFPA's Classes of Fire Alarm Paths
• 12 - How to Classify a Signal Pathway
• 13 - What is Conventional Class B Wiring?
• 14 - How Does Conventional Class A Fire Alarm Wiring Work?
• 15 - Can More Than One Class A Circuit be in a Conduit?

IDC Circuit

• 16 - What is the Quadruple Use of the Initiating Device Circuit (IDC)?
• 17 - How Does Resistance Affect the Initiating Device Circuit (IDC)?

Wiring

• 18 - Why Install Service Loops on Ceiling Smoke Detectors?
• 19 - Why is There an EOL Resistor on a Pressure Switch?

Troubleshooting

• 20 - How Do You Troubleshoot Using Supervision Voltage?
• 21 - Why Would a Smoke Detector be Wired Incorrectly?
• 22 - Is the Sense of Time Important in Troubleshooting?

Devices

• 23 - What is a Four-Wire Smoke Detector?
• 24 - What is Smoke Power on a Fire Alarm Panel?
• 25 - How do I Connect a Tamper Switch?
• 26 - How do I Wire a 10-Wire Tamper Switch?
• 27 - Why Does Closing Some Sprinkler Valves Show Trouble?

Compatibility

• 28 - What Does Listed Mean?
• 29 - Is Compatibility an Issue with Smoke Detectors?
• 30 - Can I Use a New Panel with Old Detectors?
• 31 - Is this New Control Panel Compatible with the Old System?
• 32 - Can I use Conventional Detectors on Addressable Systems?