+12V? -12V?

Think of it as two 12 volt batteries in series. From the junction of the batteries (use this as the ground refferance) you will get +12 volts on one battery and -12 volts from the other battery. Some devices using intergrated circuits are set up this way. Many of the eairly computer supplies had a -12 volt supply in refferance to the ground. The rs232 port (serial port) worked this way.

Oh! Got it now, thanks. I'd (erroneously) thought that -12V meant the negative terminal of a 12V battery.

If the + terminal is attached to ground the - terminal is then at

-12V.

Graham

A voltage never refers to "one point," unless there is a clear reference point assumed. It always refers to something of one point with respect to another, explicit or implicit, reference point.

voltage = potential difference

Best,

conect the + to ground and not the -, then the - will be below ground.

Bye. Jasen

That is the usual case that you are familiar with from cars etc however you are not limited to conecting the (-) terminal to ground/earth/chasis etc. ground is a just a usefull reference.

If you have 2 bateries in series and conect ground to the middle conection then you have both +12 and -12 available.

Colin =^.^=