The solution involves the connection of several objects. The first of which is the Signal Function object found on the Controls list under the Math Function submenu. Connect the radio or receiver object to the Signal connection point in this object. Use the +/- keys to toggle through the function field (in blue) until SigNoise appears.

Next we need to convert the signal-to-noise ratio into a Boolean value, 0 for no reception, 1 for active receive. Again go to the Math Function submenu and select a Math Function 1 object. Connect the Signal Function created above to the Input X field.

Now we need to change the Function object to get the desired result. On the Functions list create a comparator with a threshold of 0. For values >0 set the result to 1. For values 0 <= set the result to 0.

The Math Function 1 object now reflects the receive state of the radio in a 0 = Not Receiving, 1 = Actively Receiving format. This works for reception from local or network transmitters.

The output of the Math object may now be used as desired through the remainder of the model just like any other model control value.