On Jun 20, 4:51*am, klem kedidelhopper
wrote:
On Jun 19, 1:27*pm, Cydrome Leader wrote:





wrote:
Telco keeps screwing up my phone line (ca every 18mo for the pst 10yrs) and
insists they need to come in because it's my fault. Usually they cut my line
while they are installing a neighbor's line. Most recently, it prolly was the
squirrels. So, instead of removing ten gadgets to prove it's their fault, I
want a one second op

I found the earliest undivided phone line netering my house and put a 2way
2pole switch on it so I can switch from the main ingoing line to an RJ11
jack.. *but I said, why should i need to hook up a phone to this to test the
line, why not an LED.. *Ok, it seems I need 2.7K resistor in series... *seems
easy'nuff.. since it switches on only momentarily, I wonder if I'm
overkilling

So you're going to call the phone company and explain your line is bad and
you can prove it with a LED you wired into the line?

good luck with that.

And as soon as you tell them you did that they will have justification
to blame YOU for the whole damn thing, or whatever it is that you're
complaining about. You might even find a charge for a service call on
your bill as well.

If you understand anything about telephone equipment, your line sits
at 48VDC when the phone in on hook, (hung up). When it rings, an AC
voltage, usually at a frequency of 20HZ is superimposed on the line.
When you, your fax machine, or modem etc. "answers" the call your line
goes "off hook". During this condition a line "loop" current, usually
in the order of around 20ma. between your house and the central
office), commonly referred to as the CO is developed. *The central
office equipment detects this current and removes the ringing voltage,
and a conversation is established between you and the caller. At this
point your line is sitting at about 6VDC until you hang up, whereupon
the line returns to 48VDC.

An LED, (along with the appropriate series resistor) will only draw a
few milliamps from a 48V line so I don't think that it would trigger
an off hook detection, however I really don't understand what it is
you are actually trying to accomplish.

If you need an indication of the 48V look at it with a meter or just
pick up the phone and listen for dial tone. If it's a visual
indication of ringing current you need I'm sure that you can find a
schematic on line to build one, or as previously mentioned you can
just use an NE2 neon bulb with a small resistor in series. This will
draw no current until the phone rings. There are also several
commercially made units available that will do this. I would start
with Radio Shack. They used to have these. I don't know if they still
do. Keep in mind though that if anything you hang on a phone line in
any way interferes with it, and it is determined that the device was
not FCC registered, ( or probably even if it was) the phone company
can come at you full bore. Lenny

good explanation. I just reread what I posted, arrrrggg!

To find the EXACT ranges involved look for the FCC Part 68 telco
requirement [antique] that later became the IEEE??? spec

That document will tell you the EXACT ranges to expect [required] from
your telco company.

from memory holding current for the OFF HOOK state can be as high as
100mA *and* the resistor required to get that OFF HOOK status can get
really warm - if you use a resistor If you use a transistor, you need
to use a metal can type [again, for the potential heat] something like
2N2222A, or such.You can actually kill a 2N3904, plastic.

Your problem can be the house wiring. Once I had excessive noise on
the line that sounded like a stick rubbing the side of the house. I
compained and they said it was inside our building! also didn't charge
me anything to tell me that. I started removing 'legs' of the telco
wiring, until I found a section that if removed all noise went away!.
Seems the red/black wiring spool from Radio Shack had turned 'leaky'
Didn't need that section so left it out. Then the next year same type
of problem, but this time they said it was a failed pair inside one of
those huge cable bundles they string through the city underground.
They switched pairs and all was fixed.

Lesson? pretty much HAVE to be able to CUT the wiring at your house as
though you're never connected to find what's wrong, else there is
endless finger pointing.

You can do a lot with a simple voltmeter/ohmeter and switch out your
phone system. to make measurements. You can use a 9V battery to
drive your lines and check for how much current is flowing, should be
less than 10uA [again from memory] and typically less than 1uA, else
you have problems. You can check the 'balance' on your lines by
disconnecting from the telco and use the capacitance measurement to
check each line to GND - pipe or gnd in an outlet. That capacitance
should be pretty close too, else you'll have problems. That LED won't
tell you much might as well use a cheapy phone to check your line with
the rest of the house disconnected. Or, just carry a phone out to your
connection point.