Radio Shack PRO-92 owner manual Understanding Your SCANNER’S Modes, Open and Closed Modes

Models: PRO-92

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UNDERSTANDING YOUR

SCANNER’S MODES

You can program each channel with any of seven re- ceive modes. Each mode affects how your scanner op- erates when scanning and receiving transmissions, and also affects what transmissions you receive when you set the scanner to the closed mode (see “Open and Closed Modes” on Page 57). The following sections de- scribe each mode and how they affect your scanners op- eration. See “Changing the Receive Mode” on Page 45.

PL, DPL and trunking systems all use some form of cod- ed squelch. Coded squelch techniques involve the trans- mission of a special “code” signal along with the audio of a radio transmission. A receiver with coded squelch only activates when the received signal has the correct “code.” This lets many users share a single frequency, and decreases interference caused by distant transmit- ters on the same channel.

In all major metropolitan areas of the United States, ev- ery available radio channel is assigned to more than one user. Public safety radio systems on the same frequency are usually set up at a distance of 40 miles apart, or more. This means that you may hear transmissions from a distant system when your local system is not transmit- ting. By entering the PL for a local system, and operating the bank in closed mode, the scanner will not stop on transmissions from the distant system.

With few exceptions, such as the VHF Aircraft and Ma- rine bands, almost every other VHF or UHF radio system uses some form of coded squelch. By far, PL is the most popular mode among non-trunked systems. For most scanning use, try setting PL mode for all non-trunked channels. If you operate the bank in open mode, the scanner will display the appropriate code.

Open and Closed Modes

You can set your scanner to change the way it receives signals. These settings, called open mode and closed mode, affect how the scanner receives signals from communications systems that use some type of closed squelch (such as PL, DPL, LTR, MOT, and ED systems).

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About Your Scanner

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Radio Shack PRO-92 owner manual Understanding Your SCANNER’S Modes, Open and Closed Modes