Phil, I don't know the answer to the "Hijack" question. But I believe you can take a telephone with you outside to the box, plug it in any of the lines at the box and you will have bypassed all house wiring. If there's no dial tone at the box, it's the phone company's problem. If they come to your house, I suspect they'll check it the same way.

After years (maybe decades) of trouble with non-standard modems, I got two US Robotics model 5686 externals and never had another problem. Last time I saw one in a store it was $100, but they're available new & used on Ebay for short money. Should be V.90 or V.92. This is "old" knowledge. Today, there may be internals as good, I just don't know. I do know the externals always work. Good luck.

When I used dialup, I used to check my phone lines for noise using Windows HyperTerminal from a DOS prompt. I was able to get a numerical value of line noise. The telephone linemen would respect that number, and work with me to get rid of the noise, switch pairs, etc. It was important to use the line with the least noise for the computer. I believe I was using W98 at the time, I don't know if it's still possible to do this with Win XP & Vista, but FWIW here are my notes on the process. Hope it helps somebody with dialup.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 When To Suspect Line Noise
 With data calls, line noise can cause numerous problems. In general, the faster you communicate, the better your phone lines need to be. When you get up to 28.8 and 33.6 bps, it is critical that you have clear lines from end to end. Line noise can cause the following problems when trying to make high speed data connections:

                         No connection. 
                         Connection, but only "garbage" characters appear on screen.
                         Connection, but no communication. 
                         Connection, then disconnection for no apparent reason. 
                         Connection, but modem speed drops. 


                How To Check Line Noise
                Connect to a remote computer or BBS using a terminal emulation
                program such as Telix, ZTerm, or Hyper Terminal.

                Type: +++ (OK, should appear on your screen)
                Type: AT%Q (press the enter key) (you should see a number on your
                screen ranging from 000 and 255)
                Type: A/ (a few times, repeatedly) (you should see numbers each
                time you press the enter key)
                Type ATO (the letter O) to return from the command mode

                Any numbers over 30, you have considerable line noise.
                * Note: The above modem commands are not supported by all
                modem manufacturers.




-----Original Message-----
>From: Phillip Williams <[log in to unmask]>
>Sent: Aug 17, 2009 12:34 PM
>To: [log in to unmask]
>Subject: [PCBUILD] can modem hijack phone line?
>
> I have a Compaq 5000 series presario with an internal 56k modem that
>occasionally won't get a dial tone. A while back I found that after
>trying to connect, I'll close my AOL software and try my phone (on
>same line) and there isn't a dial tone. Suspecting a bad line or
>connection, I replaced all lines and connectors from the outside box.
>I still have the problem intermittantly and am wondering if it's
>possible for a dying modem to prevent a dial tone from being present.
> I haven't tallked to the local phone company yet about checking the
>line coming to the house as we have three seperate lines and this is
>the only one having problems.
>If the modem isn't a possibility as the cause, I will contact them next.
>
>Thanks,
>-Phil Williams-
>
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