Re: busying out modems
NEXUS SUPPORT (mlist@nexus.net.au)
Mon, 3 Jun 1996 23:23:05 +1000
At 10:43 AM +1000 2/6/96, Jay Hennigan wrote:
>On Sat, 1 Jun 1996, Dave Carmean wrote:
>
>> In a previous message, NEXUS SUPPORT wrote:
>> >=20
>> > Some switchs automatticlly lock out shorted lines (untill you call to=
=20
>> > request they be put back in)!
>>=20
>> The Telco always tells us this, but Jay and I have placed dead shorts for=
=20
>> probably a month, on both GTD-5 and 5ESS switches, with no such=20
>> problems.
>
>I _knew_ this would happen! Actually, the Telco has never told us this. =
=20
>Other people have said "the telephone company says not to short the=20
>lines". This is then followed by a lengthy discussion of the value and=20
>power rating of the appropriate resistor, which becomes almost a=20
>religious war.
>
>Based on loop current, the switch flags the line in one of two states. If
>the loop current is above a certain value, the line is "off-hook" or busy.=
=20
>If below a certain value (there is usually some hysteresis), it is
>"on-hook" or idle. Any resistor of a low enough value to draw sufficient
>current to flag the line as "off-hook" is functionally and logically equal
>to a short. The central office equipment automatically limits the current
>to a safe value regardless of the loop resistance which can be as low as
>zero.=20
>
>Any central office equipment that will complain about or do bad things=20
>with regard to a line which is shorted will do those identical bad things=
=20
>and complaints if the line is terminated in a resistance low enough to=20
>keep it in an off-hook state. A "permanent signal" off-hook in the=20
>ancient days of Strowger step-by-step equipment may have been a problem. =
=20
>Not any more. =20
>
>Short the line. That's how the phone company does it. On many occasions
>I've had modem lines added to the end of a hunt group, where I haven't
>been able to be there when the installer was due. I leave a note at the
>demark asking them to busy out the lines. In every case there's a nice
>little loop of jumper wire there shorting each line. In every case, I=20
>remove the wire and the line starts working immediately. =20
>
>I have left lines shorted for over a month with no ill effect, and they=20
>always come up instantly when you clear the short.
>
>ObPortmaster: One thing that _can_ cause the phone company some grief is
>when you busy out a large group of lines _at_the_same_time_. We use
>Multi-Tech racks which automatically busy the line after a programmable
>time (we use 5 seconds) when DTR is dropped. If you upgrade four full
>Portmasters and then reboot them in the middle of the night, the central
>office sees 120 simultaneous outbound calls coming up, and they all want a
>DTMF (touchtone) receiver assigned. This can result in slow dialtone for
>the central office until the dial tone times out on your modems or the
>Portmasters finish booting and assert DTR. We observed this with our
>voice line on the same CO, and it probably flagged an alarm at the office,
>but the telco never contacted us or asked us not to do it again. The same
>kind of thing happens occasionally when a radio station holds a contest,
>but in this case the tone receivers are released sooner when the people
>finish dialing. =20
>
>----
>WestNet: Internet service to Santa Barbara, Ventura and the world.=20
> 805-892-2133 805-289-1000 805-578-2121
(In Australia our switches tend to be old than US ones so this may not apply=
in the US but) A Telco technician was here four days ago and I specifically=
asked him the best way to busy out the lines. His response was to short=
them. He then said that I may have to call to arrange to have the lines=
put back in since some switches automatically lock shorted lines out. He=
said most release them immediately the short is cleared but a small number=
don't. I have also expereinced a delay of 1 hour for a line to come back=
after shorting it for 15 mins (some years ago).
Chris
Chris
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Chris Pivec
Nexus Internet Australia
Voice: +61 3 93471455, Fax +61 3 98792866
mailto:chris@nexus.net.au or mailto:postmaster@nexus.net.au
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