[OT] Comcast phone service?

[blu at vl.com (Tom Metro)]

Jerry Feldman wrote:
> 1. Digital Phone. This is what I have. Power source is supplied in the
> same manner as Verizon. Cable comes from the pole to the outside
> junction box.

The power source may be similar from the end-user perspective, in that 
you get a pair of wires with the standard 48 volts on them, but I doubt 
the manner in which those wires are powered has much resemblance to the 
classic phone company approach. Instead of your wire pair going back to 
a central office, which then has banks of batteries (or maybe just 
generators these days), the cable approach probably uses a small power 
supply hooked to the AC mains at the point where they convert from the 
coax backbone to your telephone pair. (I'd assume that point is in a 
concentrator box mounted on a pole in your neighborhood.)

The significance is that the resiliency to power failure would only be 
as good as the local AC power and any possible backup batteries in the 
concentrator box. In addition, the cable backbone was never very 
resilient to power failure because it was dependent on line amplifiers 
and pole-mounted power supplies ran from the local AC power. A local 
failure anywhere along the line between you and the head-end could knock 
out service.

However, I suspect they've redesigned their power infrastructure in 
recent years, because it's been a long time since I've seen a cable 
truck pull up in front of my house during a power failure and a guy hook 
up a small generator to the local power supply.

  -Tom

-- 
Tom Metro
Venture Logic, Newton, MA, USA
"Enterprise solutions through open source."
Professional Profile: http://tmetro.venturelogic.com/