This excerpt from page 1254 of The DCS I Gauge Companion 2nd Edtion should answer your questions regarding the DCS Remote's TMCC soft keys:
2. Considerations and Limitations of TMCC Control Using the DCS Remote
TMCC engines are controlled in the same manner as PS2 engines using the DCS Remote. They are selected from the Active Engine List and operated from the Engine Control Screen. DCS release 4.0 and later provides much improved control of TMCC engines as compared to previous releases of DCS through a revamped TMCC engine screen. New soft keys provide the DCS operator with the ability to completely emulate all of the TMCC functions available from the Lionel TMCC Cab-1 remote control. DCS release 4.0 added the following soft keys on the TMCC Engine Control Screen:
• Pressing the AX1 soft key acts the same way as it does on the Cab-1 remote control. After pressing AX1, the AX1 soft key will remain highlighted and number keys may be pressed to invoke specific TMCC functions. This allows operation of all of the features of newer TMCC engines, such as Lionel's Acela. The AX1 soft key will remain highlighted and active until it is either pressed a second time or until a different engine is selected from the Active Engine List and displayed in the DCS Remote's Engine Control Screen. Either event will turn off AX1 mode and restore the DCS Remote's keypad to normal TMCC operation
• Pressing the AX2 soft key acts the same way as it does on the Cab-1 remote control. After pressing AX2, the AX2 soft key will remain highlighted and number keys may be pressed to invoke specific TMCC functions. This allows operation of all of the features of newer TMCC engines, such as Lionel's Acela. The AX2 soft key will remain highlighted and active until it is either pressed a second time or until a different engine is selected from the Active Engine List and displayed in the DCS Remote's Engine Control Screen. Either event will turn off AX2 mode and restore the DCS Remote's keypad to normal TMCC operation
• Pressing the SPD soft key allows selection of 128 or 32 speed steps for the active TMCC engine. Only TMCC engines equipped with K-Line's speed control or TAS EOB should be used with 128 speed steps. All other TMCC engines, and Legacy engines operating in TMCC mode, should use 32 speed steps
• Pressing the MOM soft key allows selection of LOW, MED (medium) or HI (high) momentum for TMCC or Legacy engines
• Pressing the REL soft key allows toggling on and off Relative speed steps and causes the thumbwheel to act like the red knob on the CAB-1 remote. This is useful for operation of the Lionel TMCC crane car. When Relative speed steps is selected, the REL soft key will remain highlighted and REL will appear in the DCS Remote's LCD screen instead of an actual TMCC speed step number. Pressing REL a second time will restore the default Absolute speed steps and the speed step numbers will reappear.
This and a whole lot more is all in "The DCS O Gauge Companion 2nd Edition", now available for purchase as an eBook or a printed book from MTH's web store site! Click on the link below to go to MTH's web page for the book!