If the program is capable of controlling a 2nd scanner and want to 'follow' the various tgs, yes both are needed, using seperate radios. One for the discriminator output (to supply the decoding of the control channel) the other as the radio to 'follow'.
If you are just monitoring a control channel to get system information, then only 1 is needed, with just a tap. No programming cable is needed....73s Mike
