DCS Mode (DC). Radio Shack PRO-96, PRO-2096

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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When the scanner receives a transmission on a channel set to the Motorola mode, it first decodes the talkgroup ID data included with the transmission. In the Open Mode, the scanner stops on the transmission and displays the talkgroup ID on the bottom line of the display. In the Closed Mode, the scanner only stops on the transmission if the talkgroup

ID matches a talkgroup ID that you have stored in the bank's talkgroup ID list and have not locked out.

Trunking systems covered by the Motorola mode come in four categories: Type I, Type II,

Type I/II Hybrid and APCO-25. Each category displays and uses talkgroup IDs in slightly different ways.

Motorola Type I IDs are in the form FFF-SS, where;

FFF=Fleet ID

SS=Subfleet ID

Type I systems are usually organized with different user groups assigned to different fleets.

Note

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For example, a valid fleet-subfleet ID identifying all detectives within a police department might be 000-12, where 000 identifies all police users and 12 identifies the Detective division.

To properly map the raw Type I data to the correct fleet-subfleet format, you must program the correct fleet map into the scanner. Fleet map information is widely available on the Internet for most Type I systems in use.

Type II and APCO-25 system talkgroups are identified by a 5-digit number. Valid Type II talkgroup IDs are divisible by 16, while APCO-25 talkgroups are not. Use care to ensure that you enter the correct Type II IDs into your scanner. Type I/II hybrid systems use both fleet-subfleet and 5-digit formats for talkgroup IDs.

Note

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