Al salaam a'alaykum Roy

13 Dec 03 20:16, Roy J. Tellason wrote to David Drummond:

 MM>> They are _almost_ there.  The switching PSs can be run from DC, so 
 MM>> just put 10 of those monster 12 volters together!  That should last a 
 MM>> weekend or two...

 DD>> How do you achieve the -12V? You'd have to set up your 12 volters
 DD>> to produce 24V overall, with the centre tap as zero....

 RJT> You'd achieve it by doing it the way they do it now.  

They filter etc AC, this can be configured to swing negative of a centre
tap each cycle. DC just stays positive.

 RJT> With a transformer,  and appropriate rectifiers and filtering and 
 RJT> regulator...

Last time I looked, transformers and rectifiers didn't do much on DC....
Sounds like you need an inverter..

 RJT> There would be no difference on the output side -- it's only the 
 RJT> input side where things would be very different.

 RJT> How much stuff uses that -12 anyway?

The RS232 port.

Regards,
David

--- Msged/LNX TE 06 (pre)