For those that like puzzlers

[lionkingcmsl]

I am sitting at my computer, surfing the net, and my fax machine rings with an incoming call.

Now this is weird as the fax machine and the computer share the same phone line and obviously the line is being used by the computer.

The fax machine answers, but there is nothing there. No surprise there. Then the computer dumps its connection. This has happened about four times before I unplugged the phone line from the fax machine.

So I'm left to ponder, is this a virus that is trying to get into my computer, but Zone Alarm is blocking it and the fax machine sees it as a legit call and tries to intercept?

Anyone have any idea how the fax machine can "see" an incoming call when the line is already being used for an out going call by a totally different machine.

Before you ask, I do not have call waiting on this line.

Comments

[pandaguy.livejournal.com]

More than likely you are having some thunderstorms in the area, or otherwise getting some voltage spikes on the phone line which the fax machine detects as a ring signal. It is trying to answer, and this is disrupting the call/connection in progress that your computer is trying to make. No virus involved. You might want to get a phone line surge suppressor. Many power strips nowadays have them built in.

[u-t-tiger.livejournal.com]

*Cue Twilight Zone theme.

[welah.livejournal.com]

I'm with the pandaguy on this one, but I'm interested in more information: how does it ring? Is it just one ring, or many? Are the rings evenly spaced (like a normal call) or do they seem random?

If it's ringing like a normal call coming in, it's less likely that it's a natural occourance.

-Welah!

[xolo.livejournal.com]

Not a virus. Pandaguy's correct in that it's stray voltage from some source, maybe a storm. A phone *should* ring when the voltage in the line goes to +48 volts. That rise in voltage is what tells a phone (or fax machine) that a call is incoming. Depending on how sensitive your fax machine is, it may start ringing at a lower voltage. Fundamentally you're getting stray voltage on your line from some source, maybe a storm, maybe leakage from another line. If it keeps happening, call the phone company, and ask to speak to Line Repair.

Hm

[plonq.livejournal.com]

Hm. The others who have answered here are probably right, but I'm going to toss out my own theory anyway.

Is the fax machine set to answer after the first ring? If so, then I suspect your disconnect from the net is actually happening first. I am guessing that you are connecting with a Winmodem, which are notorious (especially as they get older) for spontaneous disconnects.

When the hook relay in your modem opens, thus disconnecting your modem from the line, the line voltage will rebound to 48-52 volts. If there are coils in the line, there will be considerable overshoot.

The ring detector in your fax machine sees this spike and, because it's a signal greater than a threshold (as low as 18 volts) the fax machine mistakes the spike as ring signal and it tries to answer this phantom call.

One way you can try and test this (with no guarantee, of course) is to temporarily set your modem for pulse dial and see if your fax machine tries to answer when you are dialing out.