"Simplex" refers to conventional 'radio-to-radio' function where two radios are tuned to the same frequency. As long as the radios are within range of each other and tuned to the same frequency the user will be able to push to talk and release to listen at all times.
- Positive – The use of simplex ensures that radio users within range (generally two miles or less) and tuned to the same channel will hear each other.
- Negative – Simplex dedicates the full-time use of a frequency; in other words, the resource is committed, even when no one is talking.
- The Phoenix Fire Department currently uses simplex for all tactical radio communication.
“Trunked” refers to ‘repeated’ radio function where ‘talk-out’ communication are transmitted on one frequency and ‘talk-in’ communications are received on a different frequency. This is also called ‘duplex’. The frequencies are randomly selected from a pool of available frequencies.
- Positive – The use of duplex ensures that communication can occur over large geographical areas (15-20 miles).
- Positive – Trunked radios allow a large number of radio users to have individual talkgroups (channels) while sharing a pool of frequencies over a large geographical area.
- Positive – Talkgroups (channels) can be joined together for interoperability
- Negative – The ability to communicate is dependent on the radio user’s connectivity with a repeater. If the radio cannot reach a repeater, the user will not be able to communicate
- The Regional Wireless Cooperative (RWC) is a valley-wide trunked radio system and all City of Phoenix departments except Fire are currently using the system.
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