Uniden BCD160DN English Owners Manual - Page 12

WHAT IS SEARCHING? The BCD160DN can search for active frequencies. This is different from scanning because you are searching for frequencies that have not been programmed into the scanner. When you select frequency bands to search, the scanner searches for any active frequency within the lower and upper limits you specify. When the scanner finds an active frequency, it stops on that frequency for as long as the transmission lasts. If you think the frequency is interesting, you can store it into one of the banks. If not, you can continue to search. UNDERSTANDING SCANNING What is CTCSS/DCS? Your scanner can monitor systems using a Continuous Tone Coded Squelch System (CTCSS) and a Digital Coded Squelch (DCS) system, which allow the squelch to open only when the tone you have programmed with a specific frequency is received along with a transmission. CTCSS and DCS are sub-audible tone-signaling systems sometimes referred to as PL or DPL (Motorola's trademarked terms for Private Line and Digital Private Line, respectively). CTCSS and DCS are used only for FM signals and are usually associated with both amateur and commercial two-way frequencies. CTCSS and DCS are used for many purposes. In many cases, CTCSS and DCS are used to restrict access to a commercial repeater, so that only those units which transmit the correct tone along with their signal can "talk" to the repeater. CTCSS and DCS are also used in areas that receive interference where there are several stations with output frequencies close to each other. When this occurs, you might hear multiple communications on the same frequency. The stations might even interfere with each other to the point where it is impossible to clearly receive any of the stations. Your scanner can code each received frequency with a specific subaudible CTCSS or DCS frequency or code. Then, when you receive multiple signals, you only hear the transmission with the CTCSS or DCS tone you programmed. If you do not receive the correct tone with a signal, the scanner's squelch remains closed and you hear nothing. Refer to Appendix A for tables showing the available CTCSS frequencies and DCS codes. Conventional Scanning 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 1980's, 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 12