As a fire alarm installer or technician, you’re seeking answers to how a Two-Wire Signaling Line Circuit (SLC) works.
You know that it carries signals to and from the input and output devices. However, the answers in the equipment maintenance manuals don’t really answer the question about how the two-wire SLC gets it done.
Answering questions from installers and technicians, the book “Make It Work – Understanding Signaling Line Circuits” provides insights to many of your questions about how a Two-Wire Signaling Line Circuit works.
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Frequently Asked Questions
The Signaling Line Circuit
- 1 Just What Is a Signaling Line Circuit (SLC)?
- 2 Are Addressable Fire Alarm Systems Different from Conventional Systems?
- 3 What is the Difference Between an Addressable System and a Conventional System?
- 4 What is the Difference Between Electricity Flow and Signal or Power Flow?
- 5 NFPA's 7 Classes of Fire Alarm Paths
Supervision & T-Taps on the SLC
- 6 What Is Addressable Supervision?
- 7 Is an EOL Resistor Needed for an Addressable System?
- 8 How many T-Taps are allowed on a Signaling Line Circuit (SLC)?
Programming and Addressing the Devices
- 9 How do You Use the Switches for Addressing?
- 10 Can a Control Module & Pull Station Address be Sequential?
- 11 It's the Volunteer Firefighter that Reads the Panel
Signals and Multiplexing
- 12 What are the Signals on the SLC?
- 13 Is the Signaling Line Circuit (SLC) a Data-Power Bus?
- 14 How Does Multiplexing of the Signaling Line Circuit Work?
- 15 How does an SLC Carry Both Signals and Power?
Modules and Devices
- 16 How Does the Panel Know the Address?
- 17 Why are Modules Needed in a Fire Alarm System?
- 18 What is Voltage Free Interfacing?
- 19 Can I use an Addressable Detector on a Conventional Panel?
Connecting Panels and Devices
- 20 Can an SLC Power a Horn or Strobe?
- 21 Can the Input and Output Wires on a Speaker be Reversed?
Troubles on the SLC
- 22 What Happens to the SLC when a Device is Disconnected?
- 23 Why Can't You Reset a Trouble on a Fire Alarm Panel?
- 24 Why Can't I Reset the Panel After Disconnecting the SLC?
- 25 Why Won't the Panel Show the Detectors?
- 26 How do I Fix a Damaged Loop?
Wire Length and Capacitive Lag
- 27 How does Capacitance and Shielding Affect Wiring?