I have an old lab power supply that's wired with a common and + or - 12 volts. It can also be connected as 24 volts across the + and _ terminals. The "ground" is really the center tap on a 24V DC voltage. The + terminal is "more positive" than the ground and the minus terminal is "less positive" than the ground. With such a system you could polarity reverse by switching the non-ground terminal to the + or - 12 volt tap. Somewhat cumbersome and has no advantage over a simple DPDT switch reversing the polarity of a simple 2 wire 12 volt DC output.
The exception to what I said above might be some advantage to signaling and block control, though I haven't thought it through. [EMAIL PROTECTED] wrote: > > What I mean by aDC common rail system is this: one rail is connected to > the ground and connected throughout the layout. The other rail may be > switched between + and-, depending on the direction desired. All > separation into blocks (except reverse loops and wyes) is made in the non > ground rail, which is called the control rail. That much I know. > > How does this work? My concept of "ground" is and always has been somewhat > hazy, except for vegetable gardens. > > Presumably, a system that delivers DC to locomotives and AC to action cars > etc could also be termed a common rail system, but that is not what I am > asking about. > > Tom Jarcho > > S-Trains list sponsor: http://www.americanflyertrains.com > All the Flyer you desire...books and accessories too! > > To UNSUBSCRIBE from this list send a note to [EMAIL PROTECTED] > > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ -- Chuck Smith of the NASG, Rochester Area S Gaugers (RASG) and the S Gauge Chemung Valley Lines. http://home.eznet.net/~cesmith "It is often wiser to remain silent and be thought a fool than to speak up and remove all doubt." Mark Twain S-Trains list sponsor: http://www.americanflyertrains.com All the Flyer you desire...books and accessories too! To UNSUBSCRIBE from this list send a note to [EMAIL PROTECTED] Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
