For normal tethered operation, DT402/DT400 throttles do not need a battery.
If you want to use your DT402/DT400 as an infrared or radio throttle (R & D version), you must install a 9 volt battery. You can use rechargeable batteries.
DO NOT USE ANY OTHER TYPE OF BATTERY-AA BATTERIES DO NOT WORK.
When you install the battery, the throttle will report the battery voltage and then display Idle.
Once you plug in to LocoNet, the throttles will begin operating infrared and Ds and Rs will begin operating as duplex and simplex radio throttles.
We recommend that you remove the battery from throttle if it is unplugged from the system to conserve battery life.
Batteries can be stored inside the DT402/DT400 by removing the battery and putting it back in the battery compartment with the polarity reversed.
Be careful here, see Diagram 4 for proper orientation.