Uniden BC796D APC0 25 Owner's Manual

Also see for BC 796D APCO 25: Owner's manual Owner's manual

Contents

Uniden BC796D APC0 25 Owner's Manual Manual pdf 13 page image

Trunked ScanningWhile conventional scanning worked great while there were only a few groups wanting touse the frequencies, with the advent of smaller, lower-cost radios more and more agenciesand businesses wanted to take advantage of the utility of 2-way radio. As a result, the bandsthat were used most became full, so new users were not able to take advantage of thetechnology as quickly as they wanted.Trunking solved this frequency shortage by allowing multiple groups to use the same set offrequencies in a very efficient way. While each type of trunking system operates a littledifferently (see the next few sections), they all work on the same basic premise: even in asystem with a lot of users, only a few users are ever transmitting at any one time.Instead of being assigned a frequency, as with conventional systems, each group isassigned a Talkgroup ID. A central computer controls the frequency each group operateson...and this frequency selection is made each time a user transmits. So, while on aconventional system queries, replies, and follow-ups are all on a single frequency, theycould each be on completely different frequencies on a trunked system. This semi-randomfrequency assignment made monitoring such a system impossible prior to Uniden’s inventionof the Trunktracking scanner.Motorola TrunkingWhile there are 4 different types of Motorola trunking systems, they all use the same basictrunking method. The system consists of one control channel plus one or more voicechannels (typically 10, 20, or 30 total channels). When a user presses Push To Talk (PTT)to transmit, their radio first sends their talkgroup information to the control channel. Thecomputer then assigns that talkgroup to a specific voice channel and transmits that dataover the control channel. All radios in that talkgroup switch over to the assigned voicechannel and the user can begin speaking. This all typically takes place in about asecond...the person transmitting hears a beep from their radio when the channel is assignedand it is OK to start talking.The four systems in use are:• Motorola Type I – the radios send the radio ID, the fleet and subfleet talkgroup ID to thecontrol channel each time they transmit. To program a Type I system, you need to knowthe system’s fleet map. The most common fleet maps are included at the back of thismanual. You can also find fleet map resources on the web.• Motorola Type II – the radios only send the radio ID and radio channel code to the controlchannel. The central computer keeps a database of radio ID’s and which talkgroup isassigned to which channel code for each radio, so with this system the user’s radio sendsonly about 1/3 the data as a Type I system with each transmission. Type II systems do notuse Fleet-subfleet talkgroups; instead they use a 5-digit ID for each talkgroup.• Type IIi Hybrid — these systems support a mix of both Type I and Type II users. LikeType I systems, you must know the system’s fleetmap to ensure proper tracking.• Motorola Astro Digital — for channel control purposes, this type of system operates justlike a Type II system — although the control channel can be a 3600 bps data rate (formixed analog/digital systems) or a 9600 bps (for digital-only systems). Pure digital sys-tems can be implemented under APCO 25 Phase 1 or Phase 2 standards. Your BC796Dis able to decode all unencrypted digitized voice traffic on either mixed mode or digital-onlyAPCO 25 Phase 1 systems.7