Batboard

Looking at the service manual, it looks like the M1225 receive "handset" audio on the microphone connector is at a fixed level (independent of volume knob) and the CM200/300 receive "handset" audio on the microphone connector is variable and controlled by the volume knob. I have some M1225 I've been testing with and I can confirm that the level isn't affected by the volume control on those.

Is this difference correct?

Is one or the other more common on other Radius-series radios?

I'm trying to build an accessory that can be easily plugged in, and was hoping to find fixed-level audio on an RJ-45 jack instead of the back accessory connector (accessory needs to work no matter how the user sets the volume control).

Back in the mid-1990's, when I worked at one of our local 2-way shops, we got the contract for the local mass transit or bus service, in the region. They originally had /\/\ UHF Micors, with the traditional telephone-style handset. As they upgraded their fleet, from the older Flxible Buses, to the newer Neoplan Buses, they elected to go with /\/\ UHF GM300s. We added a new cellphone-style handset, & an external speaker, to each setup. If I recall correctly, we used the microphone jack for the handset, and the rear connector for the external speaker. I believe the reed switch built into the handset was utilized to mute the external speaker audio, when the handset was removed from the cradle. With the GM300, I believe the volume of both the handset audio, as well as the external speaker were both controlled by the volume control. Albeit, the level of the handset audio was reduced considerably, so as to not be deafening to the user. There may have been a programming option, or perhaps an internal strap, to separate one to a fixed level, but we did not need that functionality, so we hadn't explored that option, if it was even available.

- trg,