-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 The Saturday 2008-06-28 at 07:58 -0400, James Knott wrote:
Carlos E. R. wrote:
RFI can be blocked with chokes. Some (many?) DC-DC converters have in fact an AC stage, with a transformer, so there is galvanic isolation. Lightning... ufff!. Dunno. Best thing is a good l. rod.
They all have an an AC stage. It's the only way you can use a transformer to efficiently change voltage. However, they tend to operate at several KHz and not power line frequencies.
Yes, but it is not the only method. Switching capacitors, for instance. Or capacitors and chokes.
There is a range of -48 V converters used in telephone exchange. They should be very expensive. And it is -48 because earth is the + line (dunno why, historical reasons, I suppose). All equipment designed for telephone exchange must use -48, but sometimes they are forced to use standard AC mains equipment with inverters. I have seen, for instance, Cisco routers fed from -48 directly.
A lot of telecom gear can be used with either + or - grounded or both sides floating. I could be wrong, but I seem to recall positive ground was used to reduce corrosion of the wires.
All the equipment I handled was only +48, but I always thought that could be changed if they wanted. Corrosion? Could be, it would make sense. I seem to recall reading about cars with positive ground in the states :-? - -- Cheers, Carlos E. R. -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.4-svn0 (GNU/Linux) iD8DBQFIaAw2tTMYHG2NR9URAoeEAJ9nzFfEXFeLrHfqVp95uMkd8UqeGgCeNmzH WJe/ftbqCgM64lO5KbAfqVE= =Z0fn -----END PGP SIGNATURE----- -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org