"mm" wrote in message
...
On Fri, 07 Apr 2006 15:32:20 -0500, Jim Redelfs
wrote:


Polarity (red or green? It doesn't matter) hasn't been
important for years.
I wasn't sad to see the issue go away. Our Central Office MDF
(Main
Distributing Frame) still has quite a number of "reversing"
heatcoils - made
specifically to reverse a line for the use of Touchtonetm!

So even a real Touchtone phone doesn't have to be connected
right
anymore? The central offices have a way to make it right even
if it
is wrong?

Is that true everywhere? or at least in Baltimore?


The "fix" is actually inside the phones that you buy. The DC
voltage is passed through a full wave rectifier so that no matter
which polarity is connected, it passes thru the bridge to the
internal cktry in the correct polarity. It's a very old phone
these days that cares about the polarity, but even some of the
old but more recent phones still have problems with ringing
detection if the polarity is reversed and won't ring properly.
Ring voltage detection, although basic, is probably the most
complex part of a simple telephone.

Ring voltage, BTW, is enough to give you a fairly good jolt, so
beware when you're handling telephone wiring.

Pop