Glossary  89
9Glossary
A
APCO The Association of Public Safety 
Communications Officials. 
The APCO Project 25 standards committee 
(http://www.apcointl.org/) defined a digital 
radio standard. The standard is often referred 
to as ‘APCO’ or ‘P25’.
C
channel In a conventional system, a channel is a pair of 
frequencies used to transmit and receive radio 
signals.
In a P25 trunking system, a channel is a group 
of radio users.
control 
channel
In a P25 trunking system, the control channel 
is used by the trunking site to let the radio 
units in the site’s coverage area know when 
they can transmit their call information.
conventional 
operation
In conventional operation, the radio is tuned 
to a programmed channel, and 
communicates with other radios either on 
that channel, or through a repeater system.
F
failsoft Failsoft operation offers P25 conventional 
operation if the radio cannot acquire a control 
channel on a trunking system for an extended 
period of time. The conventional channel may 
be a repeater channel or a direct channel.
FCC  Federal Communications Commission, an 
independent United States government 
agency that regulates interstate and 
international radio communications.