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All of this information came from the Motorola Radius Service Manual 6880101W58A circa 1988/1989 with lots of revision sheets. All of the boards listed below are used in the MaxTrac mobile radios; see the MaxTrac Detailed Service Manual for schematics. All electronic parts are interchangeable except the firmware, which governs the radio's model number and features. (You can replace the EPROM with MaxTrac firmware but then you'd need to use MaxTrac software to program it, and the model number would change.) The front panel labels and volume control knob are slightly different. The RADMBL (HVN9173 or HVN9174) DOS-only RSS package is used to program the Radius radios. These radios are all conventional; trunking was only available on the MaxTrac models.

M100 series have 2 modes. M206 series have 6 modes. M214 series have 14 modes and seem to be the only ones that offer Scanning. They require an expanded logic board (one with firmware on an EPROM). Motorola introduced the M208 and M216 series, which have 8 and 16 modes respectively. The model numbers have Revision letter B for the 8 and 16 mode radios. Channel Steering is also available on radios with the 16-pin accessory jack. The only Radius firmware IC is HLN9277A.

This is not meant to be an all-encompassing, know-all, do-all article about Motorola Radius radios. As such, there may be additional, newer information available from other sources. It's just a summary of information extracted from the above-mentioned service manual. For all intents and purposes, the Radius models mentioned here are identical to the MaxTrac 50, 100, and 300 models documented elsewhere. A lot of assemblies can be mixed, matched, and swapped between the two radio series. The radios and RSS are no longer sold but some of the more common parts are still available from Motorola.