Busy out POTS line

And if there is a problem with having a phone setting there offhook, it is a simple matter of wiring a switch across the line to busy it out (and make the phone dead as a door nail) when the switch is closed, and (just as when the phone is put back onhook) service is restored within seconds of flipping the switch to open.

Reply to
Floyd L. Davidson
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Is it possible (without leaving the phone off-hook) to busy out a POTS line so that anyone who calls the line receives a busy signal, and yet I could still dial out at anytime like I normally would? Thanks.

Reply to

A "howler".

Which is indeed intended to be the most annoying possible noise that can legally be sent over a telephone line... :-)

Older mechanical things no longer exist! Some of them also had the nasty habit of locking out the line for a *long* time after it was back onhook.

They all generate a log message of some kind, but anybody who doesn't have those sent to the bit bucket deserves the piles of paper/time wasted looking at them.

I don't think any of them would do that today, though of course there could be.

They probably don't even remove the loop current, but just monitor it. The only switch I have access to these days restores my service in less than 2 seconds.

That's a *really good* idea!

Reply to
Floyd L. Davidson

True. A 0 ohm resistor is that exact value! :-)

In all seriousness though, DO NOT put a resistor in series with the switch. It is possible that it will have to handle as much as 120 mA of current. The larger the resistance the more power it must dissipate as heat, and if the resistance is significant the heat will be too. Hence the ideal resistance is the least, which results in the least heat being dissipated.

Consider that to guarantee an offhook the resistance has to be something less that about 325 ohms (I can't remember the exact resistance, but it is in the 300-350 range). If there is 60 mA of current, that works out to 1 watt. That is enough to cause a fire. If for some reason there is 120 mA, it is 4.7 watts, which is enough to cause a fire a lot quicker!

But the heat from a 0 ohm resistor is 0, which won't even get warm.

Reply to
Floyd L. Davidson

I don't remember the exact value but it's always best to throw a certain resistance across the line.

Reply to
Tony P.

What's wrong with: Take phone off hook. Set down.

When you want to call; put it back for a few seconds, then dial.


You could forward your calls to an alway busy number, I suppose.

Reply to
David Lesher

The only "problem" I could see would be having to listen to the loud "hailer" tones (at least I always heard it called by that name) which many switches seem to put on a line which has gone off-hook but not completed a call after some brief period of time. Presumably this is to alert the subsciber that his handset had been accidentally [or otherwise] knocked off the cradle and incoming callers would receive a busy (not to mention that the offhook but idle line was wastefully tying up switch resources, like a linefinder, particularly in the older electromechanical COs) ?

it is a simple matter of wiring a switch across the

This should basically be fine, but IIRC (am I'm not sure I do), aren't there some switches which generate trouble reports, require some sort of manual intervention to restore service once the line has gone back on-hook, etc. ? Or do they just remove battery after a period of time has elapsed, and automatically restore everything back to normal once the loop has gone on-hook (e.g., opened) again for some predetermined length of time [which presumably is what you meant when you wrote "restored within seconds of flipping the switch to open" ? Just curious.

Also, I would make darn sure that the switch were in a prominent location and clearly labeled so that someone else could use the phone in an emergency if the OP were not present, incapacitated, etc.

Reply to
Justa Lurker

How about an answering machine, or the type meant for outgoing messages/announcements only, on which you record the standard busy tones , and set to answer on first ring ??


Reply to

Several things:

Leaving a phone off-hook uses power, which someone eventually has to pay for.

Phone companies don't like this, so they usually remove the feed after a while.

You can end up not being able to make outgoing calls (including emergency ones), but not realising this for a while because it doesn't happen immediately.

A continuously off-hook phone appears like a fault, which the phone company will eventually try to fix (not just to be nice - they don't make any money from faulty lines).

So, a better solution is to unplug the phone (or switch off the bell) until you want to use it. If someone happens to ring in as you try to make your outgoing call, press recall (or flash the hook) to get dialtone.

Alternatively, ask your telco to bar incoming calls.

Reply to
Phil McKerracher

You gotta be kidding. Maximum recommended loop current is 60mA, which from a 48 battery plant (that actually delivers 54 VDC), that would work out to 3 watts. Over 30 days, 24 hours a day, that is 2.3kwh. Or roughly

23 cents for a whole month of being offhook if you live where the power costs 10 cents per kwh.

They automatically put it back too, the instant you put the phone back on hook.

I'm not sure if there are any line switchers where it is not instantly done. But it is very easy to test...

Absolutely *not*. Unless you report that as a trouble, it will not even be tested, much less will there be any attempt at "fixing" it.

Why not just do *exactly* what telco people do?

That's right... take it offhook! That's standard practice.

Reply to
Floyd L. Davidson

It isn't instantaneous. After a phone has had howler tone for a certain time, it goes to lockout. The line is scanned for on-hook, but at a low rate. It may take several seconds of on-hook to restore it.


I like the turn off the ringers option. It gets the job done and doesn't cause collateral damage. Of course, it gives ring no answer, not busy.

That would work, but wouldn't be as easy to reverse as the ringers. I don't know what it would return. Maybe they would set it up as no number at all, other than for ANI. What happens if you dial an outgoing trunk's ANI number? Also, they might charge for it, or not allow it, if on a residential line.

I don't think for really extended periods of time. Sure, they busy out lines and trunks for various maintenance reasons, but they don't leave them that way in perpetuity.

Reply to
John McHarry

That depends very much on which switch. Perhaps that is scanned on some switches, but on most you'll find that the line card does it and it is not scanned. (My line is provided by a Nortel DMS-10, which definitely does not scan.)

Scanning for a state level where the entire functionality required is already built into the hardware would be waste of computing resources. That would only be done if it required some shared resource.

Offhook causes no collateral damage, and can be restored instantly without any technical skill at all.

And yes, if causing a busy condition is the intent, it requires an offhook.

I suspect most telco's would refuse to do it, or would tell the customer to simply put the phone offhook.

Manually locking out lines causes *time* loss (somebody has to unlock it), and that is money.

OGT's don't have ANI numbers. ANI associates a number to a line, not a trunk.

I've busied out lines that way and left them for *years*. It is not uncommon.

Reply to
Floyd L. Davidson

Hmm, so far, no one has asked what it is you really want to accomplish. There may be better way that suit the exact needs. For instance, it might be you just don't want to hear the ring- so a switch or phone off the hook is ok, or perhaps you want to make telemarketing calls and don't want people calling you back... Or is a "public" area and you want to let people call out, so an external switch won't do.

The phone company _can_ busy out a line yet let outgoing calls, but I don't know if they would do that on a permanent basis. For instance, if you have trouble on a line that rolls over to another line, they can busy it out until it gets repaired. I've had them do that many times.

Or you could get call forwarding and forward all cals to a non-existant number (try 000-000-0000 ?). That might cost you monthly unless you have that feature built into your calling package.


Reply to
Charles P.

It adds up when multiplied by thousands of subscribers.

Not instantly, because they can't detect if you're on hook if there's no feed.

Maybe not in Alaska, but definitely in the UK.

Reply to
Phil McKerracher

1) It is *peanuts*. 2) I based the above on worst case possible power consumption. 3) There are *not* thousands of subscribers busying out lines. 4) The cost is *far* less than if a subscriber leaves a call connection up for the same amount of time.

Instantly... try it and see.

My line is back to dial tone if I merely push the hook switch down and release it. There is no difference in how long it takes to get a dialtone between a line that is locked out or one that is not.

I'll leave it to you to realize how that can be done "if there's no feed". (Maybe I should hint that "no feed" doesn't necessarily mean no loop current. It can merely mean the line card has merely disconnected from *everything*, including the treatment that provided the howler.)

I doubt that very seriously. No phone company in the US has been interested in tracking down offhook lines since common control switching systems became ubiquitous.

(Maybe I should point out that I am retired, with more than 3 decades working in the telecom industry. I've *seen* source code and been to maintenance schools on switching systems.)

Reply to
Floyd L. Davidson

No? What makes you think that?

Tried it. No dialtone. Not all networks work like alaskan ones.

I know how it's done, I've designed SLICs. In the case I was talking about there really is no loop current. There's also a "parked" state with reduced line current.

Interesting. But it's different here.

Reply to
Phil McKerracher


So just how long *did* it take before dialtone was restored?

It has nothing to do with "Alaskan ones". Alaska is of course simply one part of the US PSTN, though granted it was way ahead of the rest of the country when it comes to digital switching, and therefore no doubt was way ahead in ignoring locked out lines too.

It depends on the manufacturer of the switching equipment. I've pointed that out more than once. My line is from a DMS-10 switch (made by Nortel). All of the DMS switches deal with line lock outs in the same basic way last time I knew...

We might note also that it is a safety issue too, because someone who needs to dial 911 can do so instantly if the lockout is released instantly. Not so if it isn't... not good.

Then you should know what's wrong with the comments you've been making...

There are several ways to accomplish the same effect. Please do not insist that everyone's line gets locked out and cannot be used because there is no loop current, that there will be thousands of lines in lockout, that the cost of electricity to provide loop current to those lines is significant, or that telco's normally initiate maintenance tickets on locked out lines.

The point is *still* that the way telco's themselves lock out an inservice telephone line typically is to simply take it offhook and leave it that way.

Frankly I don't believe you.

It doesn't make an ounce of sense to do so, and that's why nobody on this side of the pond bothers to monitor lines that go into lock out.

Reply to
Floyd L. Davidson

Depending upon your country, substitute 112, 999, 110, etc. for 911...


You should believe him. The landline telephone network outside of North America is...uh...interesting. Sometimes, it's incredibly advanced; other times, it's painfully clear that it's still a mechanical switch. And this can be in the same country!

I've also noticed that many of the same countries that adhere to variable-width landline numbers also have fixed-width wireless numbers.

"Sense" is not the discriminator; "history", "lethargy", etc. is more likely.

-- Mark --

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does not emerge from voting, party politics, or public debate. Si vis pacem, para bellum.

Reply to
Mark Crispin

A perfect description of telephone company management... ;-)

Reply to
Floyd L. Davidson


But Floyd.. Suppose I have a hunt group with multiple lines. If I short out oh 10 or 20; why I might end up burning the CO to the ground from the MASSIVE overload......

And the goons running DHS would decide I was therefore a terrorist, and send me to Gitmo.... RIGHT????

Your local loop resistance has several elements.

a) the resistance in your phone/resistor. b) The resistance of the local loop. c) The resistance of the relay coil on the line card.

Now c) may be "relay-equivalent" in a modern CO line card, but BFD.

In any case R_total will be a+b+c and even if a=0, then the total is anything but. And if the loop disperse 4.7 watts over 2.85 miles of local loop trunkage, what is the power density per foot?

And in ANY case, if some fool designed the line card to smoke because of a shorted local loop; then he shall be sent back to the Lucas works to figure out how to make computers leak oil. A line card interface should survive anything short of near-field EMP and if it does not, well, back to BORSCHT soup for lunch.

The zero ohms hysteria belongs with Craig's postcards and NYC sewergators...

Reply to
David Lesher

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