Note that Old, old Lionel TPC's (Track Power Controllers) could access MTH commands in CONVENTIONAL mode. The new-er Powermasters can also do the CONVENTIONAL mode thing. From a foggy head at this point. TPC's date to the early 1990's Part of early development of the MTH system was the copyright lawsuit, which seems rather trivial at this point.
The silver boxes.
Also note that the pictured TIU is in passive mode, only providing MTH signal to the rails. Most operators did not understand passive mode.
The 150 page operator's manual should accompany any TIU/Handheld remote set at this point. IMO, Mike CT. Some local shops did repair on these TIU's. Common problem was internal fuses that would open, requiring replacement.
