> In a previous message, NEXUS SUPPORT wrote:
> >
> > Some switchs automatticlly lock out shorted lines (untill you call to
> > request they be put back in)!
>
> The Telco always tells us this, but Jay and I have placed dead shorts for
> probably a month, on both GTD-5 and 5ESS switches, with no such
> problems.
I _knew_ this would happen! Actually, the Telco has never told us this.
Other people have said "the telephone company says not to short the
lines". This is then followed by a lengthy discussion of the value and
power rating of the appropriate resistor, which becomes almost a
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.
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.
Any central office equipment that will complain about or do bad things
with regard to a line which is shorted will do those identical bad things
and complaints if the line is terminated in a resistance low enough to
keep it in an off-hook state. A "permanent signal" off-hook in the
ancient days of Strowger step-by-step equipment may have been a problem.
Not any more.
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
remove the wire and the line starts working immediately.
I have left lines shorted for over a month with no ill effect, and they
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.
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