Emergency management can be difficult enough. Designing the systems that provide seamless communication between personnel presents some equally tough challenges.
Fire swept through the hills above the cities of Berkeley and Oakland, Calif., on Oct. 21, 1991. Known as the Tunnel Fire, it destroyed more than 2800 homes and damaged almost 700 more. It also burned some 1500 acres. And while it caused $1.5 billion in damage, its worst toll reverberated in the death of 25 people.
It was the country’s worst fire in terms of loss of life and property since the Great San Francisco Earthquake and Fire of 1906. Since then, experts have studied the Tunnel Fire to reveal strengths and weaknesses in how public safety agencies respond to catastrophes.
Multiple companies of firefighters battle such blazes according to the principle of mutual aid. For the Tunnel Fire, they came from all of the neighboring cities around San Francisco Bay. But during this fire, many companies couldn’t connect to Oakland’s fire hydrants because their cities used 2.5-in. hose couplings, while Oakland fire units used 3-in. couplings. The problem drew scrutiny in the press and in the state legislature because it was easy to grasp, and solutions seemed obvious.
Yet a parallel problem existed in 1991 and persists today. Communications systems—from first-responders’ handhelds to the networks used by dispatchers, firefighters, police, water-bomber pilots, public works personnel, and ambulance crews—are only now emerging from incompatibilities as frustrating as those hoses and hydrants.
AT THE TACTICAL LEVEL
A set of communications standards known as APCO 25, Project 25, or simply P25, has been the focus of those inconsistencies in emergency communications systems. The project was conceived by the Associated Public Safety Communications Officers (APCO), a trade association of mostly police and fire service providers, but many are now involved in the standards effort.
A universal standard must address variations in local customs (Fig. 1). For example, some fire departments place all fire-ground communications on a separate tactical channel, and the incident commander handles all communications to dispatch. Other departments want dispatch to monitor and respond directly to fireground comms.
In terms of hardware, some departments use a singlefrequency system for communications. Others have multiple frequencies and use trunking to assign channels (trunking is a term borrowed from the publicswitched telephone network).This addresses the incompatibilities that arise when police, firefighters, public works personnel, and others all rely on their own separate repeaters, which could lead to problems in a crisis situation.
Usually, the police repeater gets more use than that of the road department. But if the police use an extra repeater during an emergency, accessing the road department’s repeater may be very difficult. In a trunked system, though, any given repeater can be switched into a radio circuit as needed. Today, systems in the 700-, 800-, and 900-MHz bands are generally trunked. Below 512 MHz, trunking is allowed if it doesn’t interfere with exiting radio systems in surrounding areas.
The most up-to-date trunking systems assign priorities and share channels among agencies. When a major incident occurs, the additional talk groups automatically preempt other routine communications, making more capacity available for mission-critical messages. The lower-priority messages experience a busy signal.
Traditional non-trunked systems required additional channels to create a hierarchy of networks when there was a large incident or multiple simultaneous incidents. The problem was that some of those additional channels might already have had incumbent users, resulting in confusion and contention.
Whenever mutual-aid operations bring outside resources into a jurisdiction, there must be a method for integrating resources into communications, both when they’re dispatched and when they arrive. Of course, trunked radio systems aren’t optimal for all situations. Sometimes, it’s better to allow interior teams to off-network and use direct radio-to-radio communications and portable or vehicular repeaters.
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