intended to receive them. Within the same shared system there can be a fleet of ambulances, a fleet of police users, and a fleet of firefighters. In most shared public safety/public service systems, whether city-wide, or state/province-wide, there are often additional users sharing the system at a pre-determined lower priority for service such as animal control, public works, highways maintenance, correctional services, natural resources, etc. The system may also include talkgroups for federal agencies operating within the jurisdiction and in some cases commercial users which provide assistance to general public safety. These fleetmaps are considered subfleets of the actual talkgroups. The subfleets are intuitively programmed into the users' radios so that the users can easily find a talkgroup when s/he is required to switch for a particular situation. Alternatively, a trunking system dispatch console operator can actually 'patch' two talkgroups together making a new 'virtual' talkgroup to allow users from different agencies to communicate without having to switch channels. Generally in planning a multi-agency trunking radio system, each agency is assigned a 'block' of talkgroup ID numbers based on the number of talkgroups they anticipate requiring, plus some excess for future expansion. Thus a police service block of talkgroup ID's might begin with 102100 up to 102199, and a fire service block on the same system might begin with 102200 up to 102299. This identifies the system as 102XXX and provides one hundred talkgroup ID's for each agency. Agency-shared talkgroups (sometimes referred to as Mutual Aid or Inter-agency) may be assigned a block starting at 102500 up to 102520, allowing for twenty shared talkgroups that can be offered for use by any authorized agency. In many province-wide systems, it is mandatory for participation in the system for user agencies to include all of the authorized shared talkgroups and/or shared simplex frequencies. Scanning Most scanners that can listen to trunked radio systems (called trunk tracking) are able to scan and store individual talkgroups just as if they were frequencies. The difference in this case is that the groups are assigned to a certain bank in which the trunked system is programmed. In other words, the talkgroups are stored on the trunked bank. Comparison with telephone trunking The concept of trunking (resource sharing) is actually quite old, and is taken from telephone company technology and practice. Consider two telco central office exchanges, one in town "A" and the other in adjacent town