On Wed, 9 Feb 2011 08:39:22 +0000 (UTC), David Lesher
wrote:

boB writes:



Way back when, (back to the 70s or 60s), the polarity would reverse
when the called party answered. This was called supervision or
reversal and propagated all the way back through a long distance
connection.

Very much depended on the office involved. Panel & XY, yes; X-bar nope.
I can't recall what step did.

IIRC, step didn't reverse the line, but I don't remember the final
stages of the connector that well anymore, so it is possible it did...

Charlie
Former SxS Equipment Maintainer