9.4 Public Emergency Alarm Reporting Systems and Auxiliary Systems
Key Takeaways
- A public emergency alarm reporting system is owned and operated by the municipality or public agency and transmits alarms from publicly accessible boxes or from auxiliary connections to the communications center.
- An auxiliary fire alarm system connects a protected premises system to a public emergency alarm reporting system; the local energy type has its own power source, and the shunt type derives energy from the public system circuit.
- Public emergency alarm reporting systems require 60 hours of secondary power capacity, compared with 24 hours for a protected premises system.
- Type A systems retransmit alarms through an operator, while Type B systems retransmit automatically without operator intervention.
- Publicly accessible boxes must be identified, accessible, and maintained, and the communications center must be arranged so that alarms are received and acted upon promptly.
Why This Section Matters
Chapter 27 is in the TFM12 scope because it is part of NFPA 72 outside the excluded household chapter, and because auxiliary connections still exist in older Texas municipalities. It is also the source of one number that shows up constantly on tests: 60 hours of secondary power.
1. What a Public Emergency Alarm Reporting System Is
A public emergency alarm reporting system is a system of alarm-initiating devices, transmission channels and receiving equipment owned and operated by a municipality or other public agency, used to transmit alarms from the public to a communications center for fire or other emergency response.
Two categories of initiation:
| Category | Description |
|---|---|
| Publicly accessible alarm box | The classic street fire alarm box, accessible to any member of the public |
| Auxiliary box | Connected to a protected premises fire alarm system so that a building alarm transmits into the public system |
2. Type A and Type B Systems
| Type | How alarms are handled |
|---|---|
| Type A | The alarm is received at the communications center and retransmitted by an operator to the responding units |
| Type B | The alarm is retransmitted automatically to responding units without operator intervention |
A useful mnemonic: A = Attended retransmission; B = By itself.
3. Auxiliary Fire Alarm Systems
An auxiliary fire alarm system is the interface between a protected premises system and the public emergency alarm reporting system. NFPA 72 recognizes two arrangements:
| Arrangement | Energy source | Behavior |
|---|---|---|
| Local energy type | The auxiliary equipment has its own power source, independent of the public system | Operation of the protected premises system energizes the auxiliary transmitter, which trips the public system box |
| Shunt type | Energy is derived from the public system circuit itself | The protected premises system shunts the public circuit, tripping the box; the shunt loop is limited in length and must be supervised |
Why the distinction is tested. A shunt-type connection places the protected premises wiring electrically in series with the municipal circuit, so faults on the premises side can affect the public system. Local energy type isolates the two and is the arrangement generally preferred where either is permitted.
4. Secondary Power: 60 Hours
Secondary power durations differ by system type, and this comparison is the most commonly tested item in Chapter 27:
| System | Secondary power capacity | Then |
|---|---|---|
| Protected premises fire alarm system | 24 hours | Plus 5 minutes of alarm notification at full load |
| In-building emergency voice/alarm communications | 24 hours | Plus 15 minutes at full load |
| Supervising station facilities | 24 hours | Per Chapter 26 |
| Public emergency alarm reporting system | 60 hours | Per Chapter 27 |
Sixty hours reflects the public role of these systems: they are expected to survive a multi-day utility outage because the community depends on them when nothing else works.
5. Boxes, Supervision and Maintenance
| Requirement | Detail |
|---|---|
| Identification | Publicly accessible boxes must be conspicuously identified as fire alarm boxes and their use explained |
| Accessibility | Boxes must be accessible and unobstructed; a box behind construction fencing is out of service |
| Supervision | Transmission channels are supervised so that faults are detected at the communications center |
| Communications center | Must be arranged, staffed and powered so alarms are received and acted upon promptly, with records retained |
| Testing | Boxes, circuits and receiving equipment are inspected and tested on the schedules in Chapter 14 |
| Marking of auxiliary boxes | Auxiliary boxes are identified with the protected premises they serve |
6. Where Chapter 27 Fits Among the Chapter 26 Options
A protected premises system that transmits off site does so through one of these arrangements:
| Arrangement | Chapter | Who receives it |
|---|---|---|
| Central station service | 26 | A listed central station under contract, with runner service |
| Remote supervising station | 26 | A remote station, often at or monitored for the fire service |
| Proprietary supervising station | 26 | A station owned and staffed by the property owner for its own properties |
| Auxiliary system into a public reporting system | 27 | The municipal communications center |
In Texas, whichever arrangement is used, the monitoring firm must satisfy 28 TAC § 34.616(c): it may not monitor a Texas system for an unregistered firm, it must employ at least one technician licensee at each central station location, it must supply the five required data elements when reporting to a municipal or county emergency services center, and it must give seven days' notice before discontinuing service mid-contract.
7. Worked Fact Patterns
Pattern A. A municipality asks how long its street box system must run on secondary power after a utility failure. → 60 hours, under Chapter 27 — not the 24 hours that applies to a protected premises system.
Pattern B. An alarm arrives at a communications center and a dispatcher relays it to the responding company by radio. → Type A — retransmission by an operator. A Type B system retransmits automatically.
Pattern C. A building's auxiliary transmitter derives its operating energy from the municipal circuit itself. → Shunt type. The shunt loop length is limited and must be supervised, because a premises-side fault can affect the public circuit. A local energy type would have its own independent power source.
Pattern D. A contractor fences a construction area, enclosing a publicly accessible fire alarm box. → The box is effectively out of service. Boxes must remain accessible and unobstructed; the AHJ must be notified and interim measures arranged.
Pattern E. A Texas firm monitoring a system connected to a municipal system reports an alarm to the county emergency services center and gives only the address. → Insufficient under 28 TAC § 34.616(c)(5): the report must include the type of alarm, address, subscriber name, dispatcher identification, and call-back phone number.
What secondary power capacity does NFPA 72 require for a public emergency alarm reporting system?
What distinguishes a local energy type auxiliary fire alarm system from a shunt type?
An alarm received at a municipal communications center is retransmitted to responding units by a dispatcher. Which system type is this?