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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