Uniden UBCD996T - Manual (Page 23)

Conventional Scanning
Simplex Operation
Conventional scanning is a relatively simple concept. Each group of users in a
conventional system is assigned a single frequency (for simplex systems) or two
frequencies (for repeater systems). Any time one of them transmits, their
transmission always goes out on the same frequency. Up until the late 1980s, this
was the primary way that radio systems operated.
Even today, there are many 2-way radio users who operate using a conventional
system:
Aircraft
Amateur radio
UHF/PRS
Broadcast AM/FM/TV stations
Many business radio users
When you want to store a conventional system, all you need to know is the
frequencies they operate on. When you are scanning a conventional system, the
scanner stops very briefly on each channel to see if there is activity. If there isn’t, the
scanner quickly moves to the next channel. If there is, then the scanner pauses on
the transmission until it is over.
Simplex systems use a single frequency for both transmit and receive. Most radios
using this type of operation are limited to line-of-sight operation. This type of radio is
frequently used at construction job sites, and with inexpensive consumer radios
such as UHF/PRS radios. The range is typically 1-12 kms, depending upon the
terrain and many other factors.
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