Police Technology
Chapter Seven
Communications
Dispatch Centers
Copyright 2005 - 2009: Hi Tech Criminal
Justice, Raymond E. Foster
Learning Objectives




How hardwired and wireless universal
emergency number calls reach a public
safety answering point.
What kinds of information are
automatically included in a 9-1-1 call
Basic functions of computer aided dispatch
systems
Basic functions of an intelligent transport
system
Copyright 2005 - 2009: Hi Tech Criminal
Justice, Raymond E. Foster
Introduction
The dispatch center’s
primary purpose:
 Manage calls for service
from the public
 Provide communication
and information support
to field police officers
 Some center’s are the
first point of collection of
police statistics
Photograph provided by Gary Allen, Dispatch Monthly Magazine
Copyright 2005 - 2009: Hi Tech Criminal
Justice, Raymond E. Foster
Public Safety Answering Point
The first task of the dispatch center is to be the
public safety answering point (PSAP)
Today, 9-1-1 calls go
to the PSAP
Copyright 2005 - 2009: Hi Tech Criminal
Justice, Raymond E. Foster
Universal Emergency Number
Before 9-1-1, people
could:
 dial the operator or
 dial the police (fire,
ambulance) directly
The telephone operator was the
de facto public safety
answering point.
Copyright 2005 - 2009: Hi Tech Criminal
Justice, Raymond E. Foster
Universal Emergency Number

When 9-1-1 service began, you were
connected with your PSAP, but only
your telephone number was available
to the PSAP. No address, name, etc.
Copyright 2005 - 2009: Hi Tech Criminal
Justice, Raymond E. Foster
Universal Emergency Number

Your telephone sends out an automatic
identification number (AIN) signal (the
telephone number and a digit representing
the area code).
Think about your own
caller ID system. The
number you see on the
display is the AIN signal,
IF you pick up, you hear
the voice signal!
Copyright 2005 - 2009: Hi Tech Criminal
Justice, Raymond E. Foster
Universal Emergency Number


When a 9-1-1 call is made, the voice
signal and the AIN pass through the
local exchange carrier switch and are
routed through the 911 tandem.
The tandem reads the AIN and forwards
the call to the appropriate PSAP.
Copyright 2005 - 2009: Hi Tech Criminal
Justice, Raymond E. Foster
Universal Emergency Number


Enhanced 9-1-1 automatically queries a
telephone company database that
converts AIN information into the physical
location of the telephone.
The information on the location is the
automatic location information (ALI)
Copyright 2005 - 2009: Hi Tech Criminal
Justice, Raymond E. Foster
Universal Emergency Number
Location
Your telephone number
and location are
automatically displayed
to the PSAP operator
Screen capture provided by Crimestar, Inc
Telephone Number
Copyright 2005 - 2009: Hi Tech Criminal
Justice, Raymond E. Foster
What about cellular 9-1-1 calls?

ANI information is obtained in a similar
manner….
But, cellular telephone do not have a fixed
location…….in the past, cellular telephones
determined the default PSAP by transferring
your call to a regional agency, like the state
police.
Copyright 2005 - 2009: Hi Tech Criminal
Justice, Raymond E. Foster
Angle on Arrival (AOA).
A cellular telephone
location can be
determined using Time
Distance on Arrival and
Angle on Arrival
Copyright 2005 - 2009: Hi Tech Criminal
Justice, Raymond E. Foster
Angle on Arrival (AOA).
The signal from at least
two cell sites is used to
calculate the position of
the vehicle
Copyright 2005 - 2009: Hi Tech Criminal
Justice, Raymond E. Foster
Angle on Arrival (AOA).
Based on the position as
calculated, the cellular
system routes the call
to the appropriate
PSAP,
Copyright 2005 - 2009: Hi Tech Criminal
Justice, Raymond E. Foster
Computer-Aided Dispatch
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
Photograph provided by Randall Larson, Editor, 9-1-1 Magazine
CAD describes
software applications
and hardware that
assist in the
management of
dispatching calls for
service.
It is a management
tool that automates
the many functions of
a dispatch center.
Copyright 2005 - 2009: Hi Tech Criminal
Justice, Raymond E. Foster
Computer-Aided Dispatch
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Also provides access to other databases
and acts as interface software in the twoway voice communications between
dispatch and the field units.
Copyright 2005 - 2009: Hi Tech Criminal
Justice, Raymond E. Foster
Computer-Aided Dispatch

CAD systems are used
by many companies
that dispatch vehicles
– delivery, taxis,
buses, etc.
Photograph provided by Randall Larson, Editor, 9-1-1 Magazine
Copyright 2005 - 2009: Hi Tech Criminal
Justice, Raymond E. Foster
Computer-Aided Dispatch
Photograph provided by Randall Larson, Editor, 9-1-1 Magazine
The most important part of CAD is
the
software and various other
systems
with which CAD can interface.
 The workstation is connected
to the commercial telephone
network
 It captures information about
9-1-1 calls and field-generated
incidents – constructs a huge
relational database
Copyright 2005 - 2009: Hi Tech Criminal
Justice, Raymond E. Foster
Computer-Aided Dispatch
On the strategic side, a fully integrated
CAD system can be sued to
 Assess deployment needs
 Provide information on problem
locations
 Provide the initial incident number
that will be sued to reference all
subsequent evidence, reports, and
police activities
Photograph provided by Randall Larson, Editor, 9-1-1 Magazine
Copyright 2005 - 2009: Hi Tech Criminal
Justice, Raymond E. Foster
Some PSAPs
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
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Handle emergency calls for police, fire,
and emergency medical services
Handle the police, but transfer fire/medical
calls
Have dispatchers handling business calls
throughout the police station
Copyright 2005 - 2009: Hi Tech Criminal
Justice, Raymond E. Foster
CALL RECEIVED
Obtain Info
Yes?
Emergency?
Location?
Offense?
Verify ANI info
Weapons?
Descriptions?
Caller Info?
Update Info
Keep Caller on Line
Copyright 2005 - 2009: Hi Tech Criminal
Justice, Raymond E. Foster
E 9-1-1 provides
ANI and converts
the info into the
call for service.
Yes?
CALL RECEIVED
Obtain Info
Yes?
Emergency?
No?
Transfer?
No?
Location?
Provide info
Yes?
Offense?
Information?
No?
Weapons?
Cold Crime?
Descriptions?
No?
Caller Info?
Other Action
Update Info
Keep Caller on Line
Copyright 2005 - 2009: Hi Tech Criminal
Justice, Raymond E. Foster
Yes?
CALL RECEIVED
Obtain Info
Yes?
Emergency?
No?
Transfer?
No?
Location?
Provide info
Yes?
Offense?
Information?
No?
Weapons?
Yes?
Obtain Info
Descriptions?
Caller Info?
Update Info
Cold Crime?
No?
Offense?
Other Action
Location?
When?
Keep Caller on Line
Caller Info?
Contact at?
Copyright 2005 - 2009: Hi Tech Criminal
Justice, Raymond E. Foster
Nonemergency Points of Contact
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3-1-1: Non-emergency
telephone calls (some
jurisdictions)
4-1-1: Directory information
6-1-1: Telephone repair
Copyright 2005 - 2009: Hi Tech Criminal
Justice, Raymond E. Foster
Intelligent Transportation Systems
ITS allows dispatcher access
to real-time
Traffic information from:
 Closed-circuit television
(CCTV) cameras
 Sensors under the street.
Copyright 2005 - 2009: Hi Tech Criminal
Justice, Raymond E. Foster
Intelligent Transportation Systems

Can give emergency
responders
information on:


Nature of emergency
Best Route to location
Copyright 2005 - 2009: Hi Tech Criminal
Justice, Raymond E. Foster
Police Technology
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Copyright 2005 - 2009: Hi Tech Criminal
Justice, Raymond E. Foster