Welcome to our Digital Radio Systems information
page. This page is designed to give you an overview of public
safety digital radio technology, systems, concepts and links
to where you can learn more about digital radio communications.
The tragic events of 9/11 clarified the critical importance of effective first responder communication systems. The lack of public safety interoperability is a long-standing, complex, and costly problem with many impediments to overcome. Interoperability is the ability of public safety agencies to talk to one another via radio communication systems—to exchange voice and/or data with one another on demand, in real time, when needed and when authorized.
APCO Project 25, or "P-25" for short,
is the public safety industry standard developed by the APCO
International ( Association of Public Safety Communications
Officials) to provide a radio solution that would allow different
agencies using different radio
systems to interoperate according to a public safety industry
standard and not by system manufacturer.
The benefits for
public safety are:
- Coordinate communications with other agencies and jurisdictions.
- Purchase radios and other equipment from more than one vendor.
- Upgrade or migrate systems without replacing all your equipment.
- Share resources with other organizations to control costs.
The FCC has officially said that "digital is the mode of the future," so more and more
public safety agencies will be going digital. Digital systems are far more expensive than conventional analog systems, so I don't think that
everyone will be changing to digital anytime soon, but eventually
all public safety radio systems will go digital.
A digital radio system is basically a Project-25 digital
solution on top of a conventional
or trunked radio system. In a digital
system, a computer
converts, or " encodes", voice transmissions into
streams of data (0's and 1's - similar to a modem) and the receiving-end radio
"decodes" it back into audible voice.
Project-25 uses the IMBE ( Improved Multi-Band
Excitation) Vocoder and has two types of digital modulation
available; Project-25 Digital Trunking and Motorola ASTRO IMBE:
The above digital modulations allow for the following
four type of conventional
and trunking
digital radio systems:
-
Conventional P-25 - one frequency with digital voice.
-
Trunked at 3600 baud - digital voice with analog control
channel operating at 3600 baud. This is the most common P-25
system currently in use.
-
Mixed Mode at 3600 baud - trunked system with an analog
control channel alternating/mixing analog and digital voice
communications.
- Pure Digital at 9600 baud - trunked system
with digital analog control channel and digital voice
operating at 9600 baud.
Note: Digital radio systems can be either
simplex or repeated,
although most (but not all) are repeated.
In order to monitor and follow digitized radio transmissions, you need a
digital-capable
scanner.
Also see
our Digital
Police Scanner page for information on
digital-capable radio scanners.
| APCO
Project-25 Resources |
The following resources will provide you with everything you want to know about
APCO Project-25 radio systems and technology.
-
APCO
International - APCO (Association of Public Safety Communications
Officials) Homepage. They are the group that defines standards for Public
Safety communications in the United States.
-
APCO Project
25 Homepage - Here you can find white
papers and technical documents regarding the APCO-25 Digital
public safety project - on the APCO International Web Site.
