The fax Ma'am, just the fax.

[Mike_Duffy]

The major obstacle with diagnosing an intermittent problem is knowing how long to wait for no more such incidents before declaring that the cause is known. The problem symptoms I only notice every month or so. If I do as you say, I would need to put up with having only one phone in the house out of the dozen I normally use. Plus I would need to do so for several months.

Oh, I agree with this as well. I said my best characterisation of the sound as either a fax service or the primary tone in a baud-rate negotiation is based only on personal (& fallable) recollection. I'm not sure if you saw it, but I did mention that I already have a shoebox-sized cassette recorder with patch cord to record the phone line. I intend to use this to analyze the tone for a definitive identification. If it is a modem, then I suppose I will need to set up a dial-up networking service as well.

In fact, over the years I have noticed that occaisionally people call me me and they say that my line was 'busy' earlier when I have been home AND not using the phone. I always concluded they must have dialed incorrectly.

It may very well be that whatever is happening is going on more often, and I only notice it when someone calls simultaneously.

Seriously, thanks. You have shown me the origin of the problem.

[trader_4]

A dozen phones? Must be a 10,000 sq ft mansion. You can get a 4 handset cordless system for $40 at Costco or similar.

If it is the alarm that's answering phone calls, that sounds unusual. I think at least modern ones can be set up to be accessible from the alarm company to make updates, etc, but that should be exceedingly rare. So how it happens when someone calls you, remains a mystery. Also, once an alarm decides it needs the line, it's supposed to be set up so that it's the first thing on the house wiring, everything else comes after it. The alarm then seizes the line and cuts off everything else.

They do contact the monitoring company and how often that happens depends on how they are set up. It can range from only contacting if there is an alarm condition, to contacting every time it's armed, disarmed, etc. Is this alarm being used and monitored? If so, I would discuss with the alarm monitoring company if using VOIP is reliable and a good idea. And I know there are low cost monitoring services available, including at least one that has an internet widget with an ethernet connection on one end and what looks like a phone interface on the other. You connect it between older alarms that use a modem and your router and it then reliably sends the alarm call info to the monitoring company. I think they were charging ~$10 a month, vs $30 or more for the traditional monitoring companies. I haven't looked at modern alarm panels, but I'd suspect they must have solutions for internet connection built-in by now.

[Clare Snyder]

Just plug the base station for your cordless phone system into the fax machine and have multiple remotes - or do Like I have done with my VOIP. I just disconnected my phone wiring fromthe demarcation point and plugged the house wiring into the voip box.. If still using a POTS landline, connect the fax machine to the demarcationpoint (aka network interface)

[trader_4]

I should have added, it makes no sense that a properly working alarm system would answer calls from the alarm installer or anyone else, without you having to put it into some special mode. I'm pretty sure I remember seeing in the 100+ page manual for my alarm that there is an option for remote programming, to make changes, etc. But IDK how that would work. I would think it would require you to put the alarm into a special mode, when they are going to call. Or maybe you put it in a special mode and it calls them. Otherwise the alarm would not know which call to answer.

Also,

[micky]

I have a copier/scanner/printer/fax but it's away from the phone jack now so the fax part doesn't work.

But for the once or so a year this comes up, I use one free servive to send faxes from the PC and another to receive them.

If you email your phone number to me (remove NONONO), I'll fax you something, but it might be easier and more convenient for you to send them to yourself. To send faxes,

was still good and still free with advertising on the cover sheet, or $2 per fax with no ads, as of Dec.

2016, and the webpage looks just like it did then, 3 years ago. I guess if it works, don't break it.

To receive faxes by email I used efax.com, but maybe not more than once. Maybe never.

They used to give, iirc, so many free faxes a month, but now they just give 2 free weeks and then you're done.

[gfretwell]

I suppose you know there is a Fax program built into windoze. It is not intuitive but for a random fax now and then it works.

[trader_4]

I find it amusing that this has become focused on faxs when the OP thinks he's identified the alarm system as the likely culprit. Does anyone know of an alarm system that answers the phone or that sends or receives faxes? The ones I'm familiar with use a modem to make outgoing calls, to send information, eg an alarm condition. That they would fax seems illogical for a variety of obvious reasons.

[gfretwell]

To the best of my knowledge this was simple dial up Async or leased line Bisync in a proprietary format (when I was working) but my experience is in commercial alarm systems and not homeowner stuff.

[Clare Snyder]

Correct. Most are out-only POTS based - while many new ones run on internet or cellular - and some of THEM run diagnostics as well - self reporting - so the alarm company knows if a sensor has failed. Even MOST of those are self monitoring - not requiring any input from outside to run the tests..

[Mike_Duffy]

Either fax or modem. As you say, modem is more likely, but the fax is easier to test & eliminate as the cause.

[trader_4]

A fax from what in the house? The alarm system? The alarm isn't faxing.

[Mike_Duffy]

Faxing or attempting a dial-up connection. Elimination the possibility of a fax is easier than getting another computer to host dial-up-networking.

The only reason I suspect a fax is that is what it sounded like. But as you (I think it was you) pointed out, the fax tone sounds very much to a human ear the same as a modem's answering tone before it has detected the incoming modem.

[trader_4]

The point is that alarm systems don't fax, so screwing around trying to trick a fax machine into engaging with it is a waste. It's unlikely that would work even if it was attempting a fax. You really need to meet the tire mounting fellow.