Also known as: Motorola Type II, SmartNet, SmartZone
Motorola Type II is a classic analog trunked-radio family (marketed as SmartNet and, in its multi-site form, SmartZone) that pairs a digital control channel with analog FM voice channels. It was the dominant trunking technology for public-safety and business fleets through the 1980s, 1990s, and early 2000s, before the migration to digital P25.1 The SmartNet/SmartZone product line and its signalling are covered in more depth under SmartNet / SmartZone.
Overview
In a Type II system, one frequency is designated the control channel, carrying a continuous 3600 bit/s digital data stream. Radios idle on this channel and listen for channel grants: when a user keys up, the control channel tells every radio in that talkgroup which voice frequency to move to, they retune, pass the analog FM conversation, and return to the control channel when it ends. This is what makes the system trunked — a small pool of RF channels is shared dynamically across many talkgroups — even though the voice itself is ordinary analog FM. Each transmitting radio is identified by a radio ID, and Type II’s flat talkgroup addressing (as opposed to the older Type I “fleet/subfleet” scheme) is a defining trait. SmartZone extends the same idea across multiple sites with automatic roaming, so a radio moving between towers stays affiliated to its talkgroup.
Technical characteristics
| Property | Value |
|---|---|
| Access | FDMA with a dedicated control channel |
| Control channel | 3600 bit/s digital data stream |
| Voice | Analog FM |
| Addressing | Flat talkgroups (Type II) vs fleet/subfleet (Type I) |
| Identities | Talkgroups and radio IDs in control data |
| Multi-site | SmartZone (wide-area roaming) |
| Bands | VHF, UHF, 700/800/900 MHz |
History
Motorola introduced trunking with SmartNet in the 1980s, evolving the addressing from the earlier Type I fleet/subfleet model to the flat talkgroup model of Type II (and a transitional “Type IIi hybrid”).12 Wide-area SmartZone followed, linking multiple sites into a single logical system. The family became ubiquitous through the 1990s and early 2000s and defined how a generation of scanner users understood trunk tracking. As agencies moved to digital, Motorola’s own P25 systems and the mixed-mode SmartZone/OmniLink lineage inherited much of the same operational vocabulary.
Deployment
Type II ran a very large share of North American public-safety, transit, and commercial trunked systems for two decades. Many have since been replaced by P25, but analog SmartNet and SmartZone systems remain in service, particularly among business and utility users who never needed to migrate. Its long dominance is why so much scanner and SDR tooling — GopherTrunk included — treats Type II tracking as a baseline capability.
Decoding it with GopherTrunk
GopherTrunk locks to the Type II 3600 bit/s control channel, decodes its signalling to recover talkgroup and radio-ID activity, and follows channel grants to the analog FM voice channels to produce trunk-tracked audio — exactly the workflow a hardware trunking scanner performs, done in software from raw IQ. Because the voice payload is plain FM, no vocoder is needed; the work is in reliably demodulating and framing the control data and managing the follow-the-grant state machine. See the Status page for the current state of Type II and SmartZone support.
Sources
-
Motorola Type II — Wikipedia, for the SmartNet/SmartZone analog trunking family, its 3600 bps digital control channel, and talkgroup/radio-ID signalling. ↩ ↩2
-
Motorola Trunking — RadioReference Wiki, for Type I vs Type II addressing, control-channel behaviour, and SmartZone multi-site operation. ↩