[ILUG] Asterisk demonstration CD

[Kenn Humborg]

> >  You being a ex-telecom engineer...what's the difference between a 
> > modem
> > and a line card ?
> >
> >  They are both DSPs, I suppose...is it the ability to switch a circuit 
> > ?
> > My brain hurts, just trying to think how analog signals are routed.
> 
> Well, a modem IS a line card, of a sort, but of a specialised sort 
> which enables you to extend a serial data channel over indefinite 
> distances over an analog phone line. 

Don't forget, a line card will also generate the -48V DC supply for
a phone, generate the ring signals (70V AC, IIRC) and, these days, 
maybe even provide caller ID.  And won't fry itself if the 48V supply
gets shorted.

"Phone" sockets on modems are just pass-through connections, optionally
via a relay which allows the modem to disconnect the phone when it's
on a call.

Later,
Kenn