bud@uunet.uu.net> (06/07/91)
In article <telecom11.425.15@eecs.nwu.edu> Marc Unangst <mju@mudos. ann-arbor.mi.us> writes: > I recently had one modem in the middle of a 15-line hunt group go out. > Not wanting to move the rest of the modems up a line each, I did some > investigation with a VOM and a telephone, and discovered that plugging > a 270 ohm resistor into the phone line (across tip and ring) should > have almost the exact same effect as an off-hook telephone does -- > thus busying out the line. Now, my question is, is there anything > wrong with doing something like this? Will a 1/2W resistor be enough? > Is this an "accepted" way of busying out a phone line? The "accepted" way of busying out a line is to call your LEC and ask them to disconnect the service; they'll even stop charging you for it! Seriously, unless you have access to the CO switch internals, there is no clean way of busying a two-way loop-start subscriber line. _IF_ you have an incoming only line, what you have done should be kosher. With a two-way line, however, what you have done is to go off-hook, which the switch interprets as a request for service. When you do not provide any outgoing signaling, it will time out, and pull the cut-off relay, or the maintenence relay, or (in the case of old SXS) do nothing. Then the line just sits there, dissipating heat - in your resistor, the wires to you, and whatever relay or sensor is used in your serving CO. For a temporary thing this is not too bad, but it may also generated maintenence requests, etc, if left on for an extended period. If this line is a measured service line, you will be charged for all the time that you leave this on -- see my first paragraph. For what I perceive as a request for techno-weenie assistance: use your VOM as a milliammeter, and adjust the size of your resistor to pull 20 mA from the line. The rating (in watts) required will then be 0.0004 times the value of the resistor (in ohms). This is enough current to keep the line marked as off-hook, but minimizes the power wasted. Some of the newer CO's will show a pretty constant 30 mA for lower values of resistance. Keep raising the value until it goes down to 20 mA. Current lower than 20 mA may not work, so don't go lower. Bud Couch - ADC/Kentrox If my employer only knew... standard BS applies
John Higdon <john@zygot.ati.com> (06/11/91)
I could not RESIST adding my two cents -- plain to all of this
extensive discussion about what value resistor to busy out a phone
line with. For a quarter century, when it has been necessary to busy
out a phone line I have simply shorted it. In the case of ground
start, I have shorted it and grounded it as well. I had one trunk left
this way for about a year. Came back, pulled the short and the line
came right back to life. No CO switch, modern or ancient, gives a
hoot or a holler about what kind of load is on a line. It is all
current limited in the subscriber line equipment.
The only complaint you will ever get from telco is from the act itself
of busying out the line. This bugs some telcos more than others.
But from all this discussion, a new product idea is emerging. How
about "The Busystat". It could have an RJ11C plug on it. And it would
be guaranteed to avoid drawing excessive current on the line, avoiding
those expensive service calls.
Phooey!
John Higdon | P. O. Box 7648 | +1 408 723 1395
john@zygot.ati.com | San Jose, CA 95150 | M o o !lairdb@crash.cts.com (Laird P. Broadfield) (06/13/91)
In <telecom11.450.4@eecs.nwu.edu> john@zygot.ati.com (John Higdon) writes: > I could not RESIST adding my two cents -- plain to all of this > extensive discussion about what value resistor to busy out a phone > line with. For a quarter century, when it has been necessary to busy > out a phone line I have simply shorted it. In the case of ground > start, I have shorted it and grounded it as well. I had one trunk left > this way for about a year. Came back, pulled the short and the line > came right back to life. No CO switch, modern or ancient, gives a > hoot or a holler about what kind of load is on a line. It is all > current limited in the subscriber line equipment. Yes, John, but as we all know, you're served by a combination of an SXS and Ernestine on a cord-board. (Seriously though, folks, Pathetic*Bell really *is* nearly as pathetic as John makes them out to be.) 'Fraid though that quite a bit of CO equipment does indeed care about load on the line, as I recall a 5ESS (or was that a DMS? fuzzy memory) will drop dialtone *and* all but minimal battery on sensing a full short. Whether this will clear itself on removing the short or requires an official Service Action is a software toggle (read that as "another way for the BOC to justify a repair charge.") In fact, Keptel(Armiger)'s fancier MTUs and SNI-MTUs will perform this disconnect automatically right at your demarc; they can also be set for self-reset or requires-telco-visit-reset. Laird P. Broadfield UUCP: {ucsd, nosc}!crash!lairdb INET: lairdb@crash.cts.com
John Higdon <john@zygot.ati.com> (06/15/91)
lairdb@crash.cts.com (Laird P. Broadfield) writes: > Yes, John, but as we all know, you're served by a combination of an > SXS and Ernestine on a cord-board. (Seriously though, folks, > Pathetic*Bell really *is* nearly as pathetic as John makes them out to > be.) > 'Fraid though that quite a bit of CO equipment does indeed care about > load on the line, as I recall a 5ESS (or was that a DMS? fuzzy > memory) will drop dialtone *and* all but minimal battery on sensing a > full short. But as I may have mentioned, Ernestine is getting the boot in September and will be replaced by a 5ESS. This is to prepare for the introduction of CLASS services in the SF Bay Area in October. Also, I have ordered five more lines so that I can experiment with some of the features. (For those of you counting, this brings my total to fifteen.) In any event, I will most certainly try shorting one or two of them out and see if they come right back. (Although, you may be right; I remember having to call PB once to get a 5ESS line restored after it had been inadvertantly shorted at a broadcast remote location.) If you are correct about having to have a line manually restored after shorting it, this seems to be a very grave weakness in an otherwise capable switch, no? John Higdon | P. O. Box 7648 | +1 408 723 1395 john@zygot.ati.com | San Jose, CA 95150 | M o o !