khl@cunixc.cc.columbia.edu (Kenneth H. Lee) (05/20/89)
My setup is as follows:
Two phone lines coming into my room. Line 1 is normally used
for voice calls and line 2 is used for my modem calls.
All my jacks are wired back to an entrance bridge I have near
the telco network interfaces with 4-wire station cable. I use six
inch modular to spade lug line cords to connect from the bridge to the
telco network interfaces. Line 1 is supplied via the RED/GREEN pair
while line 2 is supplied via the BLACK/YELLOW pair of the jacks.
My problem is that when I am logged onto any system via my
dialup modem and my answering machine answers my phone, my modem drops
carrier and my session drops. I can also hear my modem carrier
whenever I use line 1 and the modem is in use.
It seems to me that the answering is causing some sort of
glitch on line 1 that is being picked up on line 2 whenever it answers
an incoming call.
Question 1: What can I do to prevent this from happening,
short of wiring a new jack which has two cables running to it, one
supplying line 1 and the other supplying line 2.
Question 2: If I had wired my jacks using twisted pair cable
instead of the 4 wire station cable, would I still be seeing this
problem? Would it make a difference if the cable were shielded?
The reason for question 2 is if I ever move into a different
place, should I wired my jacks using 4 wire station cable or with
twisted pair cable? I figure I might as well get things right the
next time around, since I will in all likelyhood have at least two
phone lines coming into my next house/apartment.
Any help or insights would be greatly appreciated. /k
Kenneth H. Lee khl@cunixc.cc.columbia.edu
Columbia University ...{topaz|rutgers}!columbia!cunixc!khl
209 Watson, 612 West 115 Street khlcu@cuvmc.bitnet
New York, NY 10025 (212) 854-8230dave@rutgers.edu (Dave Levenson) (05/21/89)
In article <telecom-v09i0170m01@vector.dallas.tx.us>, khl@cunixc.cc.columbia. edu (Kenneth H. Lee) writes: > ... Line 1 is supplied via the RED/GREEN pair > while line 2 is supplied via the BLACK/YELLOW pair of the jacks. > > My problem is that when I am logged onto any system via my > dialup modem and my answering machine answers my phone, my modem drops > carrier and my session drops. I can also hear my modem carrier > whenever I use line 1 and the modem is in use. I think there are two problems here: The answering machine is probably configured/designed to interwork with 1A2 key telephone units, and is shorting the second pair when it answers the first pair. That can probably be corrected by changing the configuration options to "SINGLE LINE" or something like that in the answering machine. If it doesn't have configuration options, modify its cord so that it only connects to one pair. The crosstalk is caused by running two lines in the same quad station wire. Use cables with two (or more) twisted pairs, and the crosstalk should be eliminated. -- Dave Levenson {uunet | rutgers | att}!westmark!dave ...the man in the mooney