[ale] OT: Comcast modem

[Alex Carver]

On 2/11/2013 07:45, Ron Frazier (ALE) wrote:

>Anyway, having the UPS there
> guarantees that my telephone will remain active for a longer time and
> internet connectivity will remain for a couple of hours if the power
> fails.  (Having internet connectivity in the event of a power failure is
> good for checking up on the weather via laptop or tablet, or sending a
> quick email, or closing down work in progress.)

It doesn't actually work that way.  The battery in the modem will give 
you a few hours of phone service (and a little less network service) in 
most cases.  But even if you put a giant generator on your modem the 
limiting factor is not your modem, it's the CMTS (or the DSLAM for the 
DSL users) power.  Most of them only have battery backup power.  If the 
CMTS is near you in terms of the power grid and goes out with your 
power, you have only the few hours of battery power on the CMTS before 
you lose everything.

If the CMTS happens to be located on a different grid that stays up when 
yours goes down then you can certainly run with phone service for an 
extended period of time.  But this is becoming less likely as time goes 
on because more CMTS are being deployed to handle subscriber density 
meaning neighborhoods may have one or more CMTS making them more 
susceptible to power failures within those neighborhoods.