University of California at Berkeley
           Department of Electrical Engineering & Computer Sciences
                    Technical and Computing Systems Support 

/share/b/pub/line-noise.help


								August 1995


	Line noise problems on dial up lines are a major problem,
for several reasons:

1- The lines are only certified for voice. This means, that, unless we
can hear audible noise on the line, we can't complain to the phone 
company.

2- The noise can be from three different places in the phone circuit:
	(a) From your house to your local switch.
	(b) From Your local switch to the campus's local switch.
	(c) From the campus switch to our modem.

3- To further aggravate the problem, Unless you are not able to tell us
which annex, and which annex port you were connected to, we can't
isolate the faulty phone line. (If you are able to make a connection,
Please write down the annex name and port number for latter reference)

However, there are certain specific problems we can address.

IF you are experiencing certain behaviors (which I will explain in
nauseating detail) then there is some hope. 

The following is a list of different types of problems. See which types
of categories your problem falls into and note the category letters.

CATEGORY		DESCRIPTION OF SYMPTOMS
_____________________________________________________________________________

  A		You ALWAYS get noise when you dial into ANY campus
		modem. ie: any number starting with (510) 642-xxxx
		or (510) 643-xxxx.

  B		You ALWAYS get noise when connected to a SPECIFIC
		Annex port. eg: every time you connect to "annex240-6 2:"

  C		You get noise on a line which usually manifests itself
		as one or two specific characters such as ! or } which
		come in bursts, from time to time throughout the entire 
		session. But, if you hang up and dial in again you 
		sometimes get a line that is completely noise free.
		(This doesn't have to be the same number, just so long
		as it has a 642 or 643 prefix.)

  D		EVERY time you dial any modem anywhere, you get noise.

____________________________________________________________________________

CATEGORY	PROBLEM  AND  WHAT TO DO
____________________________________________________________________________

  A		The problem is most likely in the trunk line between
		your exchange and the campus's. You should call your
		local telco representative and ask him kindly if he
		would please check this out for you. Be sure to ask 
		for his name and phone extension. Be extremely polite
		for best results, since they are not obligated to do
		anything for you unless you have paid for a "data" 
		grade line, which costs a lot of money, and is usually
		of no practical use for the average user.

  B		This is most likely a problem with one of our modems,
		so please send mail to dialups specifying that you get
		noise EVERY time you get that specific port.

  C		This is most likely a variation of A, but is more 
		complicated. It is probably one or more of multiple
		trunk lines connecting your exchange and ours. If
		you are convinced that this is your problem, then
		mail dialups and specify that you really believe that
		you fall into category C. I will then contact you 
		with specific instructions. If it turns out that
		it really is this type of problem, then it can be fixed.
		But it takes a lot of work!

  D		The problem is most likely to be in your modem, but
		could be in the line from your house to the local 
		switch. The first thing to try is to borrow a
		modem from a friend, and see if the problem goes away.
		if it doesn't, then borrow the terminal or PC the friend 
		was using successfully at his house, and try that. if
		that doesn't work, see if there is a box on the outside 
		of your house where the phone wire comes in. Examine it
		to see if it has a phone socket inside. (ie: one
		of those modular types that you could stick your phone
		cord into easily) (The new phone installations use
		this settup, since you are responsible for all your
		interior wiring. However, there is still a lot of
		old installations out there, which are hard wired.
		Don't touch these unless you know what you are doing.)
		if you found one, then disconnect the plug that is
		in there ( that goes to the wires in your house) and
		plug your modem modular cable into the socket, thereby
		eliminating all the house wiring. If it is still 
		noisy, then ask the phone company if they would PLEASE 
		have someone come out and check to make sure all the
		connections are tight. You will have to explain what
		you have already done (ie: swapped out the modem with
		a known good modem and terminal) and plead with them.
		If, on the other hand, it fixed the problem, then the
		problem is in the houses internal wiring, so you must
		then examine the path of the phone wire, and check to 
		see that it doesn't go by things
		like heavy motors, like refrigerators and such, 
		fluorescent lamps, and other electrical equipment.
		make sure that the wire isn't frayed, pinched,
		or otherwise deformed. (The thing to look for is
		something that might have broken the wire inside, 
		but not the insulation. This results in the wire
		barely touching inside. The voice may work ok,
		but the data will probably get munged.) If after
		checking all that, then ask the phone company if
		they would PLEASE have someone come out and check
		to make sure all the connections are tight. You
		will have to explain what you have already done
		(ie: swapped out the modem with a known good modem
		and terminal) and plead with them.

	I hope that this has been helpful.

	   -Bruce->