Dcs Mode (Dc); Motorola/Apco-25 Trunking Mode (Mo) - Radio Shack PRO-96 Owner's Manual

Many systems that use CTCSS transmit a special "turn off code" at the end of each
transmission. The turn off code causes a properly equipped receiver to mute before the
transmission ends, eliminating the "squelch tail" burst of noise the commonly occurs
when the signal is lost. CTCSS turn off code performance can be affected by weak
signals.

DCS Mode (DC)

DCS mode sets the scanner to receive transmissions using frequency modulation (FM)
with Digital Coded Squelch (DCS) subaudible data signaling. DCS is very similar to
CTCSS, except that a digital code is transmitted instead of an audio tone. Like CTCSS,
DCS allows multiple users to share a single radio frequency without hearing each other's
transmissions. In your PRO-96 scanner, the DCS feature can be used to block the
reception of transmissions on shared channel to only those that use the DCS tone that
you have specified. DCS mode also features a Code Search setting that allows you to
instantly display and store unknown codes into the channel memory. DCS data can
sometimes be heard as a low "purring" sound in the background of a voice transmission.
Some DCS systems transmit a special "turn off code" at the end of each transmission.
The turn off code causes a properly equipped receiver to mute before the transmission
ends, eliminating the "squelch tail" burst of noise the commonly occurs when the signal is
lost. DCS turn off code performance is typically more immune to weak signals than
CTCSS.

Motorola/APCO-25 Trunking Mode (MO)

You can set your scanner so it decodes the talkgroup IDs used with Motorola and
APCO-25 trunking systems and follows talkgroup calls in the trunking system. This
setting is called the Motorola mode.
Motorola systems are trunking systems used primarily by business and public safety
agencies to efficiently allocate a small number of frequencies (as few as three) to many
groups of users (as many as several thousand). To do this, each group of users in the
system is assigned to a specific talkgroup. For example, a city's east side patrol officers
might all be assigned to talkgroup 2160. One channel in the system is continuously
transmitting data that identifies which talkgroups are active on which channel. In addition,
this talkgroup information is also transmitted as subaudible data on each active channel.
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