[Asterisk-Users] FXO question

[Rich Adamson]

> >     Does somebody know how many meters of cable is supported between
> > Asterisk Digium-FXO cards and the analog telephone ?
> > Thanks,

If the two-wire interface from the FXO card follows typical telco
standards, twisted-pair cable can be up to 18,000 feet. If longer,
then load-coils are inserted to address frequency response, etc.

Telco standards are based on transmission loss, upper & lower limit
current draw, etc. The standards are not in terms of feet, but can
be translated into feet once the exact specification of the cable
is known.

The US "inside-wire" (4-wires) found in most homes and lots of 
businesses is not twisted-pair cable. Therefore, it's not typically 
recommended or used in long runs. 

Telco grade cables are oftentimes rated in terms of the number
of twists per distance. The twists tend to negate induced noise,
hum, and other electrical disturbances.

If your cabling happens to be a long run and/or the run passes by
equipment that might generate a high amount of induced noise, then
use of quality low-loss shielded cable rated for 600 ohm impedance
is often used (in the US). Its not been uncommon to see that cable 
used in telco's for long T1 cable runs, etc.