Using a modem with CDM series mobile

[adh]

Does anyone have an application note or suggested pin programming and/or cabling pinout for using a CDM series mobile with an external modem?

And also, we need to convert the 4 wire balanced line to 2 wire unbalanced for the transmit and receive data paths, would we use a bridge or a balun?

Any suggestions greatly appreciated...


adh

[Al]

If this is a voiceband modem(300-3500 Hz) the usual way to convert 2W balanced or unbalanced to 4W balanced is by use of a hybrid.
If you program the CDM for flat tx audio through the rear accessory connector, you would need to disable deemphasis at the receive radio in its programming. Depending on whether or not you have full quieting on the received carrier at the receiver point(I mean *full* quieting) you would enable or use pre and deemphasis at the transmit and receive points. The original idea behind pre and deemphasis was to reduce high frequency noise when the received signal strength was not high enough to cause full quieting in the receiver's baseband over the baseband frequency range of interest.

[adh]

Thanks Al, I suspected I would need a hybrid.

Regards, ADH