Before this:The analog trunking era: SmartNet, EDACS, LTR & MPT-1327Control-channel signaling: what the data saysTalkgroups, radio IDs & affiliation
Motorola SmartNet / SmartZone & Type II
Key takeaways SmartNet is Motorola’s proprietary analog trunking family, still very widespread. A 3600 bps digital control channel coordinates the system, but the voice is plain analog FM — digital signaling, analog audio. Radios are addressed by Type I (fleet/subfleet/size-code), Type II (flat talkgroup IDs), or Type IIi (a hybrid). SmartZone extends it across multiple sites. It is not an open standard, but it’s everywhere, and GopherTrunk decodes the 3600 bps control channel to follow calls the same way it follows a digital system.
You met the era of analog trunking earlier. SmartNet is its most successful survivor: a Motorola design from the 1980s–90s that, despite being decades old and proprietary, still carries an enormous amount of traffic across North America.
Digital control, analog voice
The defining idea of SmartNet is the split between how it’s coordinated and what it carries:
- The control channel is digital — a continuous 3600 bps data stream. It does exactly what a control channel does in any trunked system: registers radios, takes call requests, and broadcasts grants telling a talkgroup which voice channel to use.
- The voice channels are analog FM — the same modulation as a conventional analog radio. Once a radio is granted a channel, the audio there is ordinary FM you could tune by hand.
This is why SmartNet sits in this digital learning path even though its voice is analog: the signaling is digital, and following the control channel is exactly the skill the rest of the path teaches.
Type I, Type II, and Type IIi addressing
How a SmartNet system labels its users evolved over time, giving three addressing schemes you’ll encounter:
| Scheme | How radios are addressed | Character |
|---|---|---|
| Type I | Fleet / subfleet / size-code hierarchy | Older, structured; size code partitions the ID space into fleets and subfleets |
| Type II | Flat numeric talkgroup IDs | Simpler and most common; just a talkgroup number, no fleet structure |
| Type IIi | Hybrid of Type I and Type II | Supports both radio types on one system during a migration |
Type II is the one you’ll meet most. Its flat talkgroup IDs map cleanly onto the talkgroup model you already know — a number with a label, like “1808 — County Fire Dispatch.” Type I’s fleet/subfleet/size-code scheme is a holdover that takes a little decoding to map back to a meaningful unit, which is why you sometimes see Type I IDs written in a fleet-subfleet-ID notation.
SmartZone — going multi-site
A single SmartNet site covers one area. SmartZone is Motorola’s extension that networks several sites together into one logical system, so a radio can roam between sites and stay reachable on the same talkgroup. This is the same multi-site idea you’ll see again in sites, simulcast & roaming — a wide-area network built from many sites, each with its own control channel, stitched together by the back-end network.
Proprietary, but everywhere
It’s worth being clear: SmartNet/SmartZone is a proprietary Motorola system, not an open standard like P25 or the ETSI standards. There’s no public specification you can simply read; understanding it came largely from the scanner-enthusiast community reverse-engineering the control-channel signaling.
So why does so much of it remain? Cost and inertia. These systems were expensive to build, they work reliably, and many agencies kept them running for decades — sometimes as a stepping stone before migrating to P25. The result is that SmartNet remains one of the most commonly encountered trunking systems in North America, and GopherTrunk decodes its 3600 bps control channel so you can follow it like any other.
Quick check: on a Motorola SmartNet system, what kind of signal carries the actual voice?
Recap
- SmartNet is Motorola’s proprietary analog trunking family, still very widespread.
- A 3600 bps digital control channel coordinates calls, but the voice is analog FM.
- Addressing comes in Type I (fleet/subfleet/size-code), Type II (flat talkgroup IDs), and Type IIi (hybrid); Type II is most common.
- SmartZone networks multiple sites into one roaming-capable system.
- It is not an open standard, but GopherTrunk decodes the control channel to follow it like any trunked system.
Next, three more legacy families you’ll still run into: EDACS, LTR & MPT-1327.
Frequently asked questions
What is Motorola SmartNet?
SmartNet is Motorola’s proprietary analog trunking system. It uses a digital control channel running at 3600 bps to coordinate calls, but the voice itself is ordinary analog FM. SmartZone is the multi-site extension that networks several SmartNet sites together. Both remain very widespread despite being decades old.
What is the difference between Type I, Type II, and Type IIi?
They are addressing schemes. Type I organises radios by fleet, subfleet, and a size code — a hierarchical scheme. Type II uses flat numeric talkgroup IDs with no fleet structure, which is simpler and more common. Type IIi is a hybrid that supports both Type I and Type II radios on the same system during transitions.
Is SmartNet digital or analog?
It is a mix. The control channel is digital — a 3600 bps data stream that announces calls and assigns voice channels. The voice traffic itself is analog FM, the same as a conventional analog radio. So it is analog trunking coordinated by digital signaling, not a fully digital system like P25 or DMR.
Can GopherTrunk follow SmartNet systems?
Yes. GopherTrunk decodes the 3600 bps control channel to learn which talkgroup is being granted which voice channel, then follows the analog voice. Because the control channel is the map, the same follow-the-control-channel approach used for digital systems applies, even though the voice is analog FM.