Field Guide · protocol

Also known as: Connect Plus, Con Plus, MOTOTRBO Connect Plus

Connect Plus is Motorola’s proprietary multi-site DMR trunking system, part of the MOTOTRBO family, that ties several sites into one wide-area network and lets subscribers roam between them. Unlike single-site Capacity Plus, each Connect Plus site dedicates one timeslot as a continuous control channel managed by an XRC network controller, so it behaves much like a classic Tier III trunked system.12

XRC Site A Site B Site C ctrl+voicectrl+voicectrl+voice each site runs its own dedicated control channel
Connect Plus links sites through an XRC controller; every site carries its own dedicated DMR control channel for wide-area roaming.

Overview

Connect Plus was Motorola’s answer to wide-area DMR trunking before the ETSI Tier III standard and the later Capacity Max product matured. It layers a proprietary signalling and networking scheme on top of the standard DMR air interface, so the radio-frequency modulation is ordinary DMR while the trunking logic — grants, registration, and roaming — follows Motorola’s own formats. A network of sites is coordinated by one or more XRC 9000 controllers, giving subscribers seamless handoff as they move between coverage areas.

Technical characteristics

Property Value
Access Two-slot TDMA
Channel 12.5 kHz
Modulation 4FSK, 4800 baud (9600 bps)
Vocoder AMBE+2
Control Dedicated control-channel slot per site
Networking XRC controller, proprietary site linking
Signalling Motorola control-signalling blocks (variant of DMR CSBK)

The dedicated control channel is the key contrast with Capacity Plus, which instead rotates control among pooled channels using a rest channel. Because the control slot runs continuously, a scanner can lock the outbound signalling and follow channel grants much as it would on a conventional trunked system.

History

Motorola introduced Connect Plus in the late 2000s as a multi-site extension to its MOTOTRBO line, filling the gap between single-site Capacity Plus and true standardised Tier III. It saw wide deployment in commercial fleet, utility, and campus systems that needed regional coverage. Motorola later positioned Capacity Max as the strategic successor, offering larger capacity and closer alignment with the DMR standard, and has steered new deployments toward it.

Deployment

Connect Plus is common in transportation, utilities, security, and industrial fleets across North America and elsewhere, wherever an operator needed multi-site DMR coverage under a single subscriber fleet. Many of these networks remain in service even as Motorola migrates customers to Capacity Max, so Connect Plus traffic is still frequently seen on the air in the UHF and VHF land-mobile bands.

Decoding it with GopherTrunk

Connect Plus rides on the same DMR physical layer GopherTrunk already demodulates — 4FSK at 4800 baud with AMBE+2 voice — so the raw bursts and voice frames are recoverable. The trunk-following logic, however, depends on Motorola’s proprietary control-channel formats, which differ from standard Tier III signalling; support for parsing those grants and following roaming is best confirmed against the current Status page rather than assumed. Encrypted talkgroups remain out of scope, as GopherTrunk decodes clear and known-key traffic only.

Sources

  1. Digital mobile radio — Wikipedia, for the DMR air interface, its two-slot TDMA structure, and Motorola’s proprietary trunking modes built on it. ↩

  2. MOTOTRBO — Wikipedia, for the MOTOTRBO product family and the Connect Plus multi-site trunking option with dedicated control channels. ↩

See also