30 Dec
2007
30 Dec
'07
1:38 p.m.
From: mbbrutman-cctalk at brutman.com
This question is bugging me from another forum.
Is it possible to connect two modems (eg: Hayes 2400 to Hayes 2400)
using a 'dead' or isolated pair of copper wire and have them be able to
communicate?
I always thought that this can not work because the line that the modems
are connected to has to have some current. The phone system works
because an action on one end of the phone (talking into the carbon
microphone) causes a reaction on the other end. Without some sort of
current on the line, how can this work? Hence the need for 'line
simulator' circuits
Some people are claiming that it works without the line simulator. I'd
like to understand why.
(I could get out the multimeter if things get really desperate, but
maybe somebody can tell me that the line current thing only applies to
acoustically connected modems, not direct connect. Or the direct
connect modems put enough juice on the line to make it work. Or
something else that might make sense.)
Hi
The only thing missing that might be a problem is that
there is no ring generator. If you force the modems
to be off the hook, they could be just connected together.
The current is used for the carbon mike and to tell the
phone system that the phone is off the hook. Line connected
modems don't have any use for the current and only have
a load resistor there to keep the line connected.
Other than the ring detect, there is no reason two
modems can't talk to each other since they are self powered.
Dwight
_________________________________________________________________
Don't get caught with egg on your face. Play Chicktionary!
http://club.live.com/chicktionary.aspx?icid=chick_wlhmtextlink1_dec