(Note that all values used in these examples are for illustration only. You should compute the actual values to use in your studies based on good engineering judgment.)

Start with a simple example. Suppose your Talk-Out system (the fixed transmitter power and antenna gain, along with the mobile antenna and receiver sensitivity) is exactly the same as your Talk-Back system (the mobile transmit power and gain, and the fixed base station receive antenna and sensitivity). (Not a likely scenario, but useful just as a simple illustration.)

In this simplified system, since all of the system gains and losses are identical in both directions, the Talk-Back coverage would be essentially identical to the Talk-Out coverage. That means if you have computed that the required field strength for the Talk-Out system is 40dBu, you can plot a map (either in TAP or other mapping software) that shows all of the locations with 40dBu or higher to represent the Talk-Out area. And since (for this illustration) the Talk-Back system is identical to the Talk-Out system, you could plot the same level (locations with Talk-Out field strength of 40dBu or higher) to represent the Talk-Back coverage.

But suppose the Talk-Out and Talk-Back systems are identical except that the mobile transmit power is 3dB less than the base station power. That would mean that the Talk-Back system is 3dB "less efficient" than the Talk-Out system. So now, while our Talk-Out coverage can be represented by plotting all the locations where the field strength is 40dBu or higher, the "3dB less efficient" Talk-Back system would be represented by a map of the locations where the computed Talk-Out field strength is 43dBu or higher.  (You can compute the difference between the talk-out and talk-back systems with the Compute Talkback Margin function in the Utilities menu.)

By including all the differences between the two systems (as described in FAQs about Talk-Back coverage), you can determine the overall difference between the systems. The Talk-Back coverage can then be represented using the computed TAP results database but setting different levels to represent the coverage. This calculation and adjustment of levels is handled automatically when you plot the coverage in TAP and specify a "Talk-Back" plot in the Levels form.

You can make the same adjustment manually in Maptitude or other mapping software that can import dBase (.DBF) files. You can import the TAP Results Database for a study and set the Talk-Out levels to be plotted (usually with different symbols or colors). Then you can use the same Results Database imported and plotted with the adjusted field levels. In this example, the Talk-Out area would be shown as all the locations with a field strength of 40dBu and higher. Another map (or another level on the same map) showing the locations with a field value of 43dBu or above would represent the Talk-Back coverage.