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Terminology
What is Scanning?
Unlike standard AM or FM radio stations, most two-way
communications do not transmit continuously. The BC250D
scans the Frequencies you have programmed into the
Scanner’s channels until it finds an active frequency.
Scanning stops on an active frequency and remains on that
channel as long as the transmission continues. When the
transmission ends, the scanning cycle resumes until another
transmission is received.
What is Searching?
The BC250D can search each of its 27 bands to find active
frequencies. This is different from scanning because you are
searching for frequencies that have not been programmed
into your Scanner’s channels. The scanner automatically
chooses between two speeds while searching. Turbo Search,
can search the VHF FM bands at up to 300 steps per second.
What is Trunk Tracking?
Conventional scanning is a simple concept. You enter a radio
frequency in your scanner’s memory which is used by
someone you want to monitor. For example, the police in your
area may broadcast on 460.500 MHz, the fire department on
154.445 MHz, the highway department on 37.900 MHz, etc.
So when your scanner stops on a frequency, you usually
know who it is, and more importantly, you can stop on a
channel and listen to an entire conversation. This type of
scanning is easy and fun.
As the demand for public communications has increased,
many public radio users don't have enough frequencies to
meet their needs, and this has created a serious problem.
Trunking radio systems solve this problem.
In a trunked radio system, which contains up to 28 different
frequencies, radio users are divided into groups, often called
talkgroups, and these talkgroups are assigned specific IDs.
When someone in a talkgroup uses their radio, a brief burst
of data is broadcasted before each transmission. The trunking
system computer uses this data to temporarily assign each
radio in a talkgroup to an available frequency. If the group
using a frequency stops broadcasting or pauses between
replies for a few seconds, they are removed from the
BC250D 11/6/2 11:36 AM Page 7