A power master is the older tmcc way to use conventional power with a remote (cab 1) . The power master varies voltage on the rails. Two trains need blocks; just like pure conventional. DCS tui and remote can run conventional the same way as a P.Master (idont know if either does two blocks alone, I'd put my money on dcs having two line capability over a P.Master though.) A TUI can use any transformer (except maybe the MRC or CWs(?)).
Another remote option is MTH #??? ... An infrared control I think uses external power, but not 100% sure... search infrared mth & I bet you'll find out 
It's lesser known because it is limited on controlling new train features.
The use of rectification as control for two engines on one line means no whistle/bell in the train. (Whistle shack? Whistle billboard?)
.(way way back , Walthers(or Thomas) used a.c., dc, and half wave together to control various things in O (motors used the a.c., the rest I never looked into. TCA guide/list of MFGs makes a reference to it under Walthers(or Thomas)... I think it's prewar too fyi Before Lionel sued AF over O whistle relays anyhow.)
Another way is to run two throttles and isolated outside rails, one throttle for each rail and isolated drivers on the left or right of each engine. But now you need to find isolated wheels, lol. Another prewar production method lost to time.
I never stopped riding till my glasses frosted over at speed
