GE Marc V

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GE Marc V was an early trunked two-way radio system developed by General Electric Mobile Radio in the early 1980s. It was used in the United States and Australia for commercial radio networks and is now considered obsolete. Today there is only one known active Marc V system in the U.S., in Grant County, Oklahoma.

The system ran in analog FM on the 806–869 MHz band and used scan-based trunking. Radios could be set to work on more than one Marc V system, but they could not roam between different networks. Large operators ran systems as Specialized Mobile Radios (SMRs), where subscribers paid monthly per radio plus airtime.

Marc V radios came in several families, including Classic, Corona, and Centura 3C models. Some units were simple dash-mounts with a speaker and mic, while others had a telephone handset cradle. An earlier trunk-mount model appeared as Mastr, and there were MPR handhelds for Marc V. Later, Japanese-made radios began naming schemes like TMX (mobiles) and TPX (portables). Some later radios were dual-mode and could work with both Marc V and EDACS systems.

Radio networks often owned a backbone of repeaters, and individual radios could be programmed to work on different areas within a system. Radios varied from about 29 to over 100 channels, and there were limits on how many areas and channels a radio could handle. By default, radios joined the conversation on whichever area or system was active, and roaming between systems didn’t occur automatically.

Marc V used two-tone signaling to identify talk groups (groups of radios that could talk to each other). Each group had at least one tone pair, with the first tone longer to give radios time to lock on. In larger systems, a four-tone scheme (Marc V-E, enhanced) was used to reduce false signals. A continuous Busy Tone (3051.9 Hz by default) helped coordinate when a channel was in use; a “doorbell” chime alerted users when a channel became available.

Calling someone worked by pulling the microphone, the radio scanning for a free channel, and then performing a handshake with the repeater using an analog tone. If the handshake succeeded and the group tones matched, the radios in that group would all enable audio and begin transmitting. The doorbell and green ready indicator helped users know a channel was ready to talk. Some configurations allowed a “join” feature to re-enter a conversation after a interruption, but this could be disruptive.

Compared with modern trunked systems, Marc V relied heavily on tone signaling rather than a continuous control channel, which could make it less robust in busy areas. If a radio lost signal, it might miss part of a conversation unless the system reconnected it.

Border and frequency notes: some Marc V models could not be programmed for areas near the Mexican border. FCC channel assignments near the border used 25 kHz offsets, while the rest of the U.S. used 12.5 kHz offsets.