> > I disagree on the uses of the AC signal for powering the repeaters,
> > as everything I have see has network power of up to 130V DC power
> > on a separate pair of wires to the repeater.
>
> I've also always seen the repeaters powered by 130-200VDC on the
> wire.  This is partly why telco linemen will actually go to the
> trouble of "protectoring" the pairs (putting the red plastic covers
> on the punch-down positions) -- it does bad things to your test set
> if you are looking for dialtone and clip onto a T1.  I also try to
> not ground myself (i.e. leaning on a pipe) while probing a frame.

Without trying to sound too much like a commercial, I've seen ISDN repeaters
that run off of 210V DC nominal, I'm sure max is higher.  130V DC nominal is all
over the place.  There's even a Bellcore (Telcordia) standard for the acceptable
range of voltages used to power 130V DC devices.

There's at least one company that has a line Multiplexer that requires 340V DC
(maybe it's 320V DC).  I don't think this device is currently deployed in North
America, but one of the major phone companies was considering it and wanted to
be sure that our test sets didn't get damaged by it.

Most modern test sets are designed so that they can handle these high voltages.
Our latest models recognize the voltages (as well as T1 data), and will alarm
instead of drawing dialtone.  Other manufactures have similar protections in
their test sets.

-Mike

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