The PTB-100        Programming Track Booster is a handy tool for anyone who uses DCC! This        device facilitates programming as well as gives some comforting feedback        during the programming process. You will instantly know if your        decoder has received the programming instruction (or not!) by way of        indicator lights on the circuit board. So why might you want (or        need) a PTB-100?        Certain command stations allow you to read a CV during Service Mode programming,        which is useful to verify its current setting.  Sometimes trouble        reading or verifying CVs may be due to the design of the command station        and the decoder itself.  All decoders communicate back to the        command station using what's called an acknowledgement pulse, which is        defined in NMRA RP-9.2.3 as "an increased load on the programming        track of at least 60mA for at least 5ms."  Like most decoders,        SoundTraxx Digital Sound Decoders generate the acknowledgment pulse by        momentarily applying power to the motor.
        If the decoder is otherwise working properly (i.e., responds properly on        the mainline to speed and direction commands), but the command station        is having troubles reading CV data from the decoder, it may be due to        incompatibilities between the electrical requirements of the sound        decoder (which are different from conventional decoders due to the added        audio circuitry) and the electrical characteristics of the programming        track.