Adding duplex radio, infrared or simplex radio to your existing Digitrax system is simple because of LocoNet.
InfraRed
You probably already own a DT300, DT400, UT4 or DT402 series throttle. All of these are "InfraReady." These all come with two IR emitters pre-installed. All you have to add for IR operation is one or more UR90 Infrared Receivers to your layout. Most layouts require multiple UR90s because the infrared signal is line of sight. This means that your receiver will need a sight path to the throttles.
Simplex Radio
Digitrax throttles with an "R" at the end of the part number are simplex radio throttles. DT402R, DT400R, UT4R are examples of this type of control. With simplex radio, the throttles send signals to one or more UR91 Simplex radio receivers mounted on the layout. Generally layouts need only a single UR91 but sometimes more are added to improve operation in special cases.
The UR91 simplex radio receiver also has an infrared receiver built in so that users with IR throttles can run at the same time as simplex throttles. Note the UR91 DOES NOT support duplex radio operation.
Digitrax radio equipped starter sets are no longer available with the simplex option however, the components for simplex are available individually.
DT400, DT402 and UT4 series throttles without radio can be upgraded to simplex or duplex radio operation for a fee. See the throttle product page for the model you own for more information.
Duplex Radio
Digitrax throttles with a "D" at the end of the part number are duplex radio throttles. DT402D & UT4D are examples of this type of control. With duplex radio, the throttles send and receive signals to and from one or more UR92 Duplex radio transceivers mounted on the layout. Generally layouts need only a single UR92 but sometimes more are added to improve operation in special cases.
The UR92 duples radio transceiver also has an infrared receiver built in so that users with IR throttles can run at the same time as duplex throttles. Note the UR92 DOES NOT support simplex radio operation.
Digitrax strongly recommends that new users choose the duplex option because it is much more flexible than the older simplex technology. Digitrax radio controlled starter sets are only sold with Duplex capablilties.
DT400/R, DT402/R and UT4/R series throttles can be upgraded to duplex radio operation for a fee. See the throttle product page for the model you own for more information.
LocoNet
Digitrax LocoNet makes adding tetherless control as simple as plugging in a component or two. Because of the system architecture, there is no need to upgrade your existing command station or booster hardware.
All three types of tetherless control and walk around wired control can operate simultaneously on your LocoNet layout. In that scenario, you would need a UR92, a UR91, one or more UR90s and one or more UP5s installed on the layout to be able to host all types of tetherless and walkaround control. That means that all your friends can operate together, no matter what type of control they use at home.