You don't need duplex to operate switch machine decoders. You DO need a DT40x throttle of some sort, the UT4 cannot operate accessory decoders.
Simplex has a bit more range and better battery life, but if you operate in public venues were other clubs may use NCE, it's utterly useless, the NCE radios swamp the band used by Digitrax Simplex. Duplex operates on 2.4GHz with multiple channels so there generally are not interference issues.
If you have neither and want to add radio, probbaly best to get Duplex. If you currently have Simplex and are otherwise happy with it, no reason to switch.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Duplex allows you to acquire/dispatch locos w/o having to plug into the system among other things. It's probably worth the extra money. Duplex eqpt doesn't work on simplex receivers--you can check it out on the Digitrax website, lots of good info. If you use your throttle to control switches, it's definitely worth the extra money, imo.
Richard
Simplex radio is "one-way" communication. It can send data but cannot receive data.
Duplex radio is "two-way" communication that can both send and receive data.
Rich
Alton Junction
Digitrax has simplex and duplex radio options. What is the difference?