Security Alarm Considerations

If I install the dsl modem as usual, using filters only on the phone device, before contacting the alarm company, what kind of behavior can I expect? I would hope that the dsl circuit would work fine but would render the alarm system ineffective until the proper alarm filter was installed. Is this correct?

-Frank

A. ask your alarm company.

B. have your dsl provider install a pots splitter

C. install your own pots splitter (should be instructions at

Take your choice.

What alarms typically (and should) do is literally "seize the line" by opening a relay between the outside connection and all internal connections which allows it to hang up on any existing call before calling the alarm company. Given this setup your best bet is to put a DSL splitter/filter just after the NID (phone companies box) and split the line into voice and data. But many alarm guys don't like this because this allows something plugged into the "data" side to tie up the line if things aren't done right or if equipment fails. So they want to put their box ahead of the splitter. Which can degrade the DSL signals. Two lines are the EASIEST way to resolve this. Or deal with an alarm company that is reasonable and has equipment that will not muck up the DSL.

YMMV

There is really no way to know what will happen. There are a long list of things that can go wrong.

By the way, having your alarm company install an alarm-specific DSL filter is, IMO, one of the worst possible solutions. It still requires passing the DSL signal into the alarm box, where it runs unshielded around the alarm's circuit board.

DS

no synch (i.e., no dsl) and noise on the phones.

The alarm may work normally.

You need a filter/spliter or "POTS" between your NID and alarm/phone wiring. The alarm uses voice frequency signals and will not be stopped by your DSL signal.

Thanks for your reply. I've since talked with the alarm company and know how I will approach this. I'm gonna get an alarm filter (RJ31 Jack).

The alarm guy says that without the filter, dsl will work, but there will be a potential problem with the alarm not being able to seize the line, if necessary. The alarm company sells the filter for 53 + shipping. I found one on-line for 19.95 + shipping. I'll order it.

Mainly I wanted to know that I could get this installed, tested, and then put the alarm filter in later. I guess I should be able to.

Yep. I may disconnect it until I get the right filter.

-Frank

Until a clueless plugs a phone into the jack trying to make a call. It WILL happen.

It depends on the alarm system. Effectively, it is an unfiltered phone. If it has high impedence, then there may not be much effect at all. If it has capacitance/inductance, then it could kill DSL dead.

Alarms are usually wired _in series_ [upstream] of all the other housephones. Many [all?] will answer the phone after

10-12 rings. Otherwise, they're callout devices that will disconnect all housephones when they do.

You should be able to disconnect the alarm system (jack near the control unit) and have DSL function fine with microfilters. These jacks pass-in/pass-out wiring, so a standard filter will not work, or if it does, it will filter the whole house.

Short of special alarm filtering, I'd go with an NID splitter, and make sure the DSL side cannot go "off hook".

-- Robert

I recommend against this approach, unless superior techniques are not practical. The problem is that your DSL signal will run into the alarm box. The DSL lines are unshielded and the alarm box is the alarm's shield. So any noise generated by the alarm circuit board (which is often substantial) will couple right into your DSL.

It depends what he's imagining without the filter. There are dozens of right and wrong ways to wire an alarm system and DSL without an alarm filter.

Yes, you can. But you should only do this if it's impossible to separate a long run of wire past the alarm that must carry both the DSL signal and the telephone signal. Otherwise, you should separate them before the alarm.

DS

If you don't care, don't sweat it.

In my experience, alarm filters are many times worse than cheap minifilters. The problem is not the filter itself, but that the DSL signal is being run into and then out of the alarm box. The alarm box *is* the alarm's shield.

If all you want is for it to work, cheap filters are fine.

DS

I'll test and find out.

I have found, in my own experience, that the hype (and benefits) about a home run are highly exaggerated. Small or no difference in most cases. I know there are those that incessantly run speed tests 4 or 5 times a day and complain if they see a drop in performance. But for everyone of those folks there are 50 that don't really notice any difference between 128Kbps and

1.5Mbps. Especially if all they do is surf.

Filters have worked fine for me up to now.

We'll see.

-Frank

Some people buy a Rolex, some buy a Timex. Often, both people are satisfied. Life is all about priorities. Routine stuff.

-Frank

Right, but if they were both about the same price, only idiots would buy Timexes. Well, maybe not since part of owning a Rolex is being able to say you own a Rolex. But the point is, when you have solutions that are generally equally expensive and equally difficult and one is definitively superior to the other, does it really matter how much superior it is or whether people need the superiority?

DS

I was wondering how long it would take you to start the name calling when someone didn't agree with you. I can handle the disagreement. Can you?

-Frank

Umm, who exactly did I call an idiot? It was a hypothetical person who purchased an inferior product when a superior one was available at the same price. It wasn't you. It wasn't someone taking a position you took.

I made no criticisms or implications about your character. On the other hand, you implied that I cannot handle a disagreement.

DS

I know.

-Frank

So.. then, "idiots" refers to who?

-Frank

Home runs are a commonly recommended solution due to the unknown nature of what's behind the walls, under the floor, in the attic, through the mouse nest, etc... Especially if you're not on site. If I hadn't done my own rewiring of the phone lines in my house and been an early adopter my DSL service would likely have been terrible with all the quad wire mess with bad splices and such all over everywhere and 40 years old.

As it was I got DSL back when the actual phone company did a truck roll. The guy showed up and I told him I wanted him to put in a new NID in a new location. He said he couldn't do that. Against policy. So I showed him my then current NID under the porch behind the gas meter and he took about 10 seconds to change his mind and do it as I suggested. :)