EMC188 Intro to Trunking 1/3 To: Emergency Communications Units - Information Bulletin To: Emergency Management Agencies via Internet and Radio By: Auxiliary Communications Service (ACS) of the California Governor's Office of Emergency Services EMC188 Intro to Trunking 1/3 For release 6/15/99 AN INTRODUCTION TO TRUNKING RADIO SYSTEMS By Mike Krueger, N6MIK, Assistant Radio Officer, Training Officer, County of Orange RACES "The concept of a trunking radio system was first developed in the mid-1980's for the commercial radio business. More and more business customers required radio communications, while fewer and fewer frequencies remained to issue. Motorola designed the first trunking system to help alleviate the congestion in the LMR spectrum, and allow more users to share the same frequencies by way of dynamic re-use. Trunking is a method of using relatively few communication paths for large number potential users. This article will concentrate on the Motorola systems, due to their popularity among California public safety agencies. These radio systems are similar to the telephone trunking concept that has been in use for years. There are currently three types of Motorola trunking systems in use by public-safety agencies: Type I, Type II and Type IIi. A Type I system is the oldest and least robust of the Motorola trunking formats and has a limited user capacity. The newer and much more complex Type II, or SmartNet, system abolishes Subfleets and introduces the Talkgroup (TG). This type of system is very popular among public safety because of increased security, emergency signaling, and remote radio monitoring and control. Type II systems are capable of up to 4,000 talkgroups, 65,535 individual radio identifiers, and up to 28 system repeaters. A typical Type I trunked radio system, which is also called Privacy Plus, consists of five to seven radio repeaters connected by a central controller. A Type I system defines its "channels" by using Fleet and Subfleets. For example, a city fire department may be on one fleet and the public works department may be on another fleet, with up to 16 subfleets per fleet. Subfleets are referred to by letter, A~O, and are the "channels" of a Type I system. The Central Controller is the computerized brain of the trunked system and performs many functions, the most obvious of which is letting users talk by managing the talkgroups and system repeaters. The controller also allows for administrative functions, such as adding talkgroups, radios, or repeaters, changing the trunking parameters, billing, and other functions. The central controller uses one of the system's repeaters to transmit a constant data stream (3600-baud FSK) on the control channel. This stream is encoded with a 4-digit hexadecimal system identifier and sends instructions to radios on the system. The control channel usually rotates daily among a set group of channels to avoid making one repeater do all the work." Continues next bulletin. --- To subscribe to bulletins, use the Subscription Services web page at . If you don't have web access, just send an e-mail message to . - For training assistance contact the ACS Training Officer at the web site or send an email to larton@garlic.com - Submit suggestions, topics or comments on the bulletins to cary.mangum@macnexus.org or cary_mangum@oes.ca.gov Bulletins are on the ACS Web page: http://acs.oes.ca.gov -and a Landline BBS: 916-262-0856 (graphical & standard interface); and a FTP Archive: ftp.ucsd.edu/hamradio/packet/tcpip/incoming for some bulletins. For earlier ones: ftp.ucsd.edu/hamradio/races