Line monitoring is an essential part of 100V line speaker systems which form the part of a fire and evacuation system. It allows monitoring of each speaker zone circuit for open and short circuit faults by measuring the impedance of the line. This allows the user to centrally monitor the status of each speaker zone ensuring its good operation.
Many fire alarm systems allow for line monitoring to be directly hooked up to the main fire board of the building, alternatively a unit such as the Redback A 4567B or A 2065 may be installed to provide a convenient central hub for line monitoring.
What is required for a line monitoring circuit?
There are a couple of important requirements for a speaker circuit to be suitable for line monitoring. These are:
- All speakers must be fitted with a 22uF bipolar capacitor in series with the transformer. These are typically fitted as standard on fire/evac or EWIS speakers.
- A terminating resistor must be fitted at the end of the speaker string (typically 100kΩ).
- Star wiring, tee offs or multi-feed speaker circuits are not permitted. Redback line monitoring units will not operate correctly with these configurations.
Example System Wiring for Redback A 4567B.
Looking for Redback line monitoring products?
A 4567C • Line Monitoring Unit 10 Zone
Specifically designed to monitor the condition of 100V line speaker systems in emergency paging and fire evacuation installations. Many large commercial installations have speaker circuits in excess of 250W. Traditional line monitoring units were limited to 50W per zone and would not handle this load. The A 4567C can handle loads up to 500W per zone.
S 4457 • 100V Line Evac Override Relay Box
Designed primarily for PA speaker line installations with two PA systems active in a building. Useful for applications where a dedicated evac speaker system is running along side a dedicated background music system. This box allows the background music to be disconnected when the evac system is active. It can also be used to switch between two different PA systems with only one output speaker line. Requires 24V DC power source (sold separately).
A 4567C • 10 Zone Line Monitoring Unit
Specifically designed to monitor the condition of 100V line speaker systems in emergency paging and fire evacuation installations. Traditional line monitoring units were limited to 50W per zone and would not handle this load. The A 4567B can handle loads up to 500W per zone.
