Please forgive me for my lack of radio intellect.
The "dual-head" simply means that it will be a VHF radio as always. It would be like the Motorola radios that WSP has had for years. (I believe the regular model is the x-9000, but unsure) They have been replaced with Kenwood mobiles.
The "dual-head" simply means that there are two speakers. The one on the drivers side is the "area" radio and the speaker on the passenger side if for the other selected channel and "scan."
The microphone then has a PTT button similar to a rocker switch, in that it moves up and down. The down position is on the "area" channel and the up position is selected on the radio head.
A great web-site that shows the older CHP radios that started this is
http://www.mbay.net/~wb6nvh/chpradio.htm