PS-1 is a more sophisticated version of QSIindustries electronic reverse and sound systems designed for MTH locomotives. It was called "Proto-Sounds." After PS-2 command systems came out, the term "PS-1" was used.
QSI designed all its products for Lionel Electrical Operating Standards (L.E.O.S.). Most layouts had postwar Lionel transformers. A ZW was the ultimate power source. It's perfect for PS-1 systems.
Electronic transformers were in their infancy and command control was years away. Some PS-1 systems can work with newer transformers and some can't.
Like Gilly, I installed BCR's in all my PS-1 locomotives. They run like Hamilton watches. Apply 10 volts (no more) for 60 seconds and a locomotive is ready to run, no matter how long it has been stored.
The Website for BCR's is www.jandwelectronics.com Wayne Renga repairs and upgrades PS-1 and PS-2 systems.
The QSI Website is www.the-scaled-tin-rail.com
When buying any locomotive with PS-1, make certain it runs. If not, it could have a scrambled chip or damaged/fried circuit board(s). As Gilly posted, consider additional cost of any repairs or upgrades when bidding.
Generally, PS-1 locomotives command low prices but in an auction anything can happen. Bids depend on who is interested and cash on hand.