Supervising station monitoring: communication paths and timing
Which kind of station is actually under contract, how fast the signal has to arrive, and why the router in the closet matters as much as the panel battery.
A monitored fire alarm is only as good as the path between the panel and the people watching it. NFPA 72 Chapter 26 sets the rules for that path: who is allowed to receive the signals, how fast they have to arrive, and how the connection itself is supervised.
Which kind of station
| Arrangement | What defines it |
|---|---|
| Remote supervising station | Signals go to a communications center meeting NFPA 1221, to a fire station or a governmental agency responsible for responding, or, only where the AHJ permits, to a listed central supervising station. The owner gives the AHJ annual documentation naming who is responsible for inspection, testing and maintenance. |
| Central station service | Six elements under one contract: installing the transmitters, monitoring, retransmission, record keeping and reporting, testing and maintenance, and runner service, from a prime contractor listed for it. |
| Proprietary supervising station | Trained, competent personnel in constant attendance, responsible to the owner of the protected property. |
A contract that monitors but does not retransmit is not central station service. Documentation of compliance is posted within 3 ft of the control unit, naming the prime contractor, the system as installed, the issue and expiry dates and the listing organization. A monitoring room unstaffed overnight is not a proprietary supervising station.
From the field
Owners and AHJs use the term central station loosely. Ask which arrangement is actually contracted and listed, then look for the posted document by the panel.
The 90 second limit
From initiation at the premises, through transmission, to display and recording at the supervising station takes no more than 90 seconds. Recording is part of the 90 seconds, not something that follows it.
Supervising the path
- One path: supervised at intervals of no more than 60 minutes, with a failure annunciated at the station within 60 minutes.
- Several paths: each supervised within 6 hours, failure annunciated within 6 hours, and arranged so a single point of failure cannot take out more than one path.
That last condition is the one that catches two paths sharing a single cable. The tight interval is why single path cellular has to check in so often.
Dialers
A DACT uses one telephone line plus a one way private radio alarm system, a two way RF multiplex system, or another transmission means meeting the general communications requirements. A second phone line is still permitted, but only where none of those is available at the premises, the AHJ approves, and the dialer calls a second receiver number when the first fails.
The dialer connects ahead of any private phone system. On transmitting it seizes the line, drops any call in progress and holds the line until it is done. On a failed transmission it retries at least 5 and no more than 10 times, then shows a failure at the premises.
From the field
Take a phone off hook, then put the panel into alarm. A dialer that waits politely for the line to free up does not comply.
Power for the communicator
Transmitters and shared equipment the signal depends on, such as a router or modem, carry at least 24 hours of secondary power. Shared equipment may drop to 8 hours only with AHJ acceptance and a supporting risk analysis.
From the field
A panel with 24 hours of battery feeding a router on unswitched utility power is not monitored after a power cut.
Changing providers
When signals move to a new supervising station, the new station notifies the customer and the AHJ in writing within 30 calendar days after the change. A supervising station also notifies the AHJ before terminating service.
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