Before this:Trunking flavors: dedicated vs. distributed, message vs. transmissionThe analog trunking era: SmartNet, EDACS, LTR & MPT-1327
EDACS, LTR & MPT-1327
Key takeaways Three legacy trunking families you’ll still meet. EDACS (GE/Ericsson/Harris) uses a fast dedicated 9600 bps control channel and AFS — Agency/Fleet/Subfleet numbering, with a digital ProVoice voice option. LTR (Logic Trunked Radio) is unusual: no dedicated control channel — low-speed sub-audible data rides on every repeater, so control is distributed, with variants LTR-Net and Passport. MPT-1327 is the British/European standard with a 1200 bps control channel, used widely internationally. All three are mostly analog FM voice with digital signaling.
Beyond Motorola’s SmartNet, three other legacy families filled the analog-trunking world. Each solved the trunking problem differently, and each has a recognisable fingerprint on the air.
EDACS
EDACS — Enhanced Digital Access Communications System — came from General Electric, passing through Ericsson and then Harris as the product line changed hands. Its hallmarks:
- A fast, dedicated control channel running at 9600 bps — quicker than SmartNet’s 3600 bps or MPT’s 1200 bps, which made EDACS feel snappy in assigning channels.
- AFS talkgroup numbering — Agency / Fleet / Subfleet — a three-level hierarchy that organises talkgroups by agency, then fleet within it, then subfleet, rather than a flat number.
- Voice is usually analog FM, but a digital variant, ProVoice, exists for systems that wanted digital audio over the EDACS infrastructure.
EDACS was a serious public-safety and utility contender in its day and you’ll still find systems running.
LTR
LTR — Logic Trunked Radio — takes a genuinely different approach to everything else in this path. There is no dedicated control channel at all.
Instead, low-speed sub-audible data is carried on every repeater, riding along below the voice on each channel. The trunking logic is distributed across all the channels rather than centralised on one control frequency: each repeater announces its own status, and radios use that scattered data to find and follow calls. This makes LTR systems cheaper and simpler to build — there’s no separate control channel to dedicate — but it means the “control” information is spread out rather than sitting in one place.
Common variants you’ll meet:
- LTR-Net — a networked, multi-site evolution of basic LTR.
- Passport — another LTR variant with its own roaming and numbering features.
MPT-1327
MPT-1327 is a British signaling standard (the “MPT” prefix comes from the UK Ministry of Posts and Telecommunications) that became the dominant trunking standard outside North America. It uses a 1200 bps control channel and analog FM voice.
For decades MPT-1327 was the go-to for commercial and government fleets across Europe, Africa, Australia, Asia, and Latin America — taxi companies, utilities, transport, and public services. Its international ubiquity is roughly the role SmartNet played in the US. You’re most likely to meet it if you monitor outside North America.
Telling them apart
| System | Control channel | Talkgroup numbering | Origin | Where common |
|---|---|---|---|---|
| EDACS | Dedicated, 9600 bps (fast) | AFS (Agency/Fleet/Subfleet) | GE → Ericsson → Harris | US public safety, utilities |
| LTR | None — distributed sub-audible on every repeater | Home repeater + ID | Specialised mobile radio | Business, light commercial |
| MPT-1327 | Dedicated, 1200 bps | Prefix + ident | UK (MPT) | International, outside North America |
The quickest fingerprints: EDACS has a fast dedicated control channel; LTR has no dedicated control channel to find at all (look for sub-audible data on the voice repeaters); and MPT-1327’s slower 1200 bps control channel turns up mostly outside the US. As always, the surest identification is letting a decoder read the control-channel signaling once it’s locked.
Quick check: which of these systems has no dedicated control channel?
Recap
- EDACS (GE/Ericsson/Harris) uses a fast 9600 bps dedicated control channel and AFS numbering, with a digital ProVoice option.
- LTR has no dedicated control channel — control is distributed as sub-audible data on every repeater; variants include LTR-Net and Passport.
- MPT-1327 is the British/European standard, 1200 bps control channel, used widely internationally.
- All three carry mostly analog FM voice with digital signaling.
- Tell them apart by control-channel behaviour — or let the decoder identify the signaling.
Next, we lighten up with the smaller digital modes you’ll meet on the bands: dPMR, D-STAR & System Fusion.
Frequently asked questions
What is EDACS?
EDACS (Enhanced Digital Access Communications System) is a trunking family from GE, later Ericsson and Harris. It uses a fast dedicated 9600 bps control channel and an AFS — Agency/Fleet/Subfleet — talkgroup numbering scheme. Voice is usually analog FM, though a digital variant called ProVoice exists.
How is LTR different from other trunking systems?
LTR (Logic Trunked Radio) has no dedicated control channel. Instead, low-speed sub-audible data is carried on every repeater alongside the voice, so the trunking control is distributed across all the channels rather than centralised on one. Variants include LTR-Net and Passport.
What is MPT-1327?
MPT-1327 is a British signaling standard for analog trunking, widely used internationally outside North America. It uses a 1200 bps control channel and analog FM voice. It was one of the most common trunking standards in Europe, Africa, Australia, and elsewhere for commercial and government fleets.
Are these systems still in use?
Yes, though they’re legacy and shrinking as operators migrate to P25 and DMR. EDACS, LTR, and MPT-1327 systems still run in various regions, and a scanner enthusiast still meets them. Recognising each by its control-channel behaviour is a useful skill.