LED spec for phone line?

I want to put an LED to test my phone line, which I found to be ca 50v.

Where/how do I find the right LED?

THe LEDs at Radio Shack are all like 2v (yea I remember VCC of 2.3 on diodes
in my EE2 for non EEs course).

Should I just use a regular bulb, like the kind used for Christmas lights,
instead? (what about the LEDs used for CHristmas lights? Shouldn't they
work?)

Besides, I really only want ONE LED.

- = -
Vasos Panagiotopoulos, Columbia'81+, Reagan, Mozart, Pindus, BioStrategist
http://www.panix.com/~vjp2/vasos.htm
---{Nothing herein constitutes advice. Everything fully disclaimed.}---
[Homeland Security means private firearms not lazy obstructive guards]
[Urb sprawl confounds terror] [Phooey on GUI: Windows for subprime Bimbos]

 

[mike]

On 6/17/2012 4:32 PM, vjp2.at@at.BioStrategist.dot.dot.com wrote:

I want to put an LED to test my phone line, which I found to be ca 50v.

Where/how do I find the right LED?

THe LEDs at Radio Shack are all like 2v (yea I remember VCC of 2.3 on diodes
in my EE2 for non EEs course).

Should I just use a regular bulb, like the kind used for Christmas lights,
instead? (what about the LEDs used for CHristmas lights? Shouldn't they
work?)

Besides, I really only want ONE LED.

- = -
Vasos Panagiotopoulos, Columbia'81+, Reagan, Mozart, Pindus, BioStrategist
http://www.panix.com/~vjp2/vasos.htm
---{Nothing herein constitutes advice. Everything fully disclaimed.}---
[Homeland Security means private firearms not lazy obstructive guards]
[Urb sprawl confounds terror] [Phooey on GUI: Windows for subprime Bimbos]




A series resistor will answer your question.

Assume you now all about what happens when you load a phone line.

 

[Arfa Daily]

"mike" <spamme9@gmail.com> wrote in message
news:jrlqog$1cl$1@dont-email.me...

On 6/17/2012 4:32 PM, vjp2.at@at.BioStrategist.dot.dot.com wrote:
I want to put an LED to test my phone line, which I found to be ca 50v.

Where/how do I find the right LED?

THe LEDs at Radio Shack are all like 2v (yea I remember VCC of 2.3 on
diodes
in my EE2 for non EEs course).

Should I just use a regular bulb, like the kind used for Christmas
lights,
instead? (what about the LEDs used for CHristmas lights? Shouldn't they
work?)

Besides, I really only want ONE LED.

- = -
Vasos Panagiotopoulos, Columbia'81+, Reagan, Mozart, Pindus,
BioStrategist
http://www.panix.com/~vjp2/vasos.htm
---{Nothing herein constitutes advice. Everything fully
disclaimed.}---
[Homeland Security means private firearms not lazy obstructive
guards]
[Urb sprawl confounds terror] [Phooey on GUI: Windows for subprime
Bimbos]




A series resistor will answer your question.
Assume you now all about what happens when you load a phone line.

And of course what happens when a ring signal appears across the line ...

Arfa

 

[gregz]

<vjp2.at@at.BioStrategist.dot.dot.com> wrote:

I want to put an LED to test my phone line, which I found to be ca 50v.

Where/how do I find the right LED?

THe LEDs at Radio Shack are all like 2v (yea I remember VCC of 2.3 on diodes
in my EE2 for non EEs course).

Should I just use a regular bulb, like the kind used for Christmas lights,
instead? (what about the LEDs used for CHristmas lights? Shouldn't they
work?)

Besides, I really only want ONE LED.

- = -
Vasos Panagiotopoulos, Columbia'81+, Reagan, Mozart, Pindus, BioStrategist
http://www.panix.com/~vjp2/vasos.htm
---{Nothing herein constitutes advice. Everything fully disclaimed.}---
[Homeland Security means private firearms not lazy obstructive guards]
[Urb sprawl confounds terror] [Phooey on GUI: Windows for subprime Bimbos]

They are all pretty much the same except for current requirement. Most will
light with less than 5 ma. Know ohms law ?

Greg

 

[hr(bob) hofmann@att.net]

On Jun 17, 6:32 pm, vjp2...@at.BioStrategist.dot.dot.com wrote:

I want to put an LED to test my phone line, which I found to be ca 50v.

Where/how do I find the right LED?

THe LEDs at Radio Shack are all like 2v (yea I remember VCC of 2.3 on diodes
in my EE2 for non EEs course).

Should I just use a regular bulb, like the kind used for Christmas lights,
instead? (what about the LEDs used for CHristmas lights? Shouldn't they
work?)

Besides, I really only want ONE LED.

                                    - = -
 Vasos Panagiotopoulos, Columbia'81+, Reagan, Mozart, Pindus, BioStrategist
                   http://www.panix.com/~vjp2/vasos.htm
  ---{Nothing herein constitutes advice.  Everything fully disclaimed..}---
   [Homeland Security means private firearms not lazy obstructive guards]
 [Urb sprawl confounds terror] [Phooey on GUI: Windows for subprime Bimbos]

Are yo trying to use the phone line to light an LED and save
electricity???? The led will make it look like you want to make a
phone call and will get the phone company disconnecting your line in
short order. If you only want the led to glow dimly, then use a
series resistor to limit the current to 1-2 milliamperes. That may
not be enough to trigger the phone company circuits into believing you
want phone service.

BUY A BATTERY!

 

[spamtrap1888]

On Jun 17, 5:33 pm, "Arfa Daily" <arfa.da...@ntlworld.com> wrote:

"mike" <spam...@gmail.com> wrote in message

news:jrlqog$1cl$1@dont-email.me...









On 6/17/2012 4:32 PM, vjp2...@at.BioStrategist.dot.dot.com wrote:
I want to put an LED to test my phone line, which I found to be ca 50v..

Where/how do I find the right LED?

THe LEDs at Radio Shack are all like 2v (yea I remember VCC of 2.3 on
diodes
in my EE2 for non EEs course).

Should I just use a regular bulb, like the kind used for Christmas
lights,
instead? (what about the LEDs used for CHristmas lights? Shouldn't they
work?)

Besides, I really only want ONE LED.

    - = -
  Vasos Panagiotopoulos, Columbia'81+, Reagan, Mozart, Pindus,
BioStrategist
   http://www.panix.com/~vjp2/vasos.htm
   ---{Nothing herein constitutes advice.  Everything fully
disclaimed.}---
    [Homeland Security means private firearms not lazy obstructive
guards]
  [Urb sprawl confounds terror] [Phooey on GUI: Windows for subprime
Bimbos]

A series resistor will answer your question.
Assume you now all about what happens when you load a phone line.

And of course what happens when a ring signal appears across the line ...

Reminds me that back in the day, the radio studio phone had two lights
that flashed instead of a ringer. The lights looked like a salt and
pepper set. Maybe the OP could put a neon lamp across the phone line.

 

[Michael A. Terrell]

On 6/18/2012 10:52 AM, spamtrap1888 wrote:

Reminds me that back in the day, the radio studio phone had two lights
that flashed instead of a ringer. The lights looked like a salt and
pepper set. Maybe the OP could put a neon lamp across the phone line.

Or some old 400 series KTU cards from a PBX system. I still see
complete 1A2 systems from time to time.

 

[hr(bob) hofmann@att.net]

On Jun 18, 9:52 am, spamtrap1888 <spamtrap1...@gmail.com> wrote:

On Jun 17, 5:33 pm, "Arfa Daily" <arfa.da...@ntlworld.com> wrote:





"mike" <spam...@gmail.com> wrote in message

news:jrlqog$1cl$1@dont-email.me...

On 6/17/2012 4:32 PM, vjp2...@at.BioStrategist.dot.dot.com wrote:
I want to put an LED to test my phone line, which I found to be ca 50v.

Where/how do I find the right LED?

THe LEDs at Radio Shack are all like 2v (yea I remember VCC of 2.3 on
diodes
in my EE2 for non EEs course).

Should I just use a regular bulb, like the kind used for Christmas
lights,
instead? (what about the LEDs used for CHristmas lights? Shouldn't they
work?)

Besides, I really only want ONE LED.

    - = -
  Vasos Panagiotopoulos, Columbia'81+, Reagan, Mozart, Pindus,
BioStrategist
   http://www.panix.com/~vjp2/vasos.htm
   ---{Nothing herein constitutes advice.  Everything fully
disclaimed.}---
    [Homeland Security means private firearms not lazy obstructive
guards]
  [Urb sprawl confounds terror] [Phooey on GUI: Windows for subprime
Bimbos]

A series resistor will answer your question.
Assume you now all about what happens when you load a phone line.

And of course what happens when a ring signal appears across the line ....

Reminds me that back in the day, the radio studio phone had two lights
that flashed instead of a ringer. The lights looked like a salt and
pepper set. Maybe the OP could put a neon lamp across the phone line.- Hide quoted text -

- Show quoted text -

It depends on what he wants the leds to do, light up the room, or only
light up when the phone is ringing. 50 years ago I designed the telco
circuits that detected when a customers wanted service. It was a pain
to distinguish between a real off-hook from the customer and line
leakage due to poor cable insulation, squirrels, etc.

 

[spamtrap1888]

On Jun 18, 10:53 am, "hr(bob) hofm...@att.net" <hrhofm...@att.net>
wrote:

On Jun 18, 9:52 am, spamtrap1888 <spamtrap1...@gmail.com> wrote:









On Jun 17, 5:33 pm, "Arfa Daily" <arfa.da...@ntlworld.com> wrote:

"mike" <spam...@gmail.com> wrote in message

news:jrlqog$1cl$1@dont-email.me...

On 6/17/2012 4:32 PM, vjp2...@at.BioStrategist.dot.dot.com wrote:
I want to put an LED to test my phone line, which I found to be ca 50v.

Where/how do I find the right LED?

THe LEDs at Radio Shack are all like 2v (yea I remember VCC of 2.3 on
diodes
in my EE2 for non EEs course).

Should I just use a regular bulb, like the kind used for Christmas
lights,
instead? (what about the LEDs used for CHristmas lights? Shouldn't they
work?)

Besides, I really only want ONE LED.

    - = -
  Vasos Panagiotopoulos, Columbia'81+, Reagan, Mozart, Pindus,
BioStrategist
   http://www.panix.com/~vjp2/vasos.htm
   ---{Nothing herein constitutes advice.  Everything fully
disclaimed.}---
    [Homeland Security means private firearms not lazy obstructive
guards]
  [Urb sprawl confounds terror] [Phooey on GUI: Windows for subprime
Bimbos]

A series resistor will answer your question.
Assume you now all about what happens when you load a phone line.

And of course what happens when a ring signal appears across the line ...

Reminds me that back in the day, the radio studio phone had two lights
that flashed instead of a ringer. The lights looked like a salt and
pepper set. Maybe the OP could put a neon lamp across the phone line.

It depends on what he wants the leds to do, light up the room, or only
light up when the phone is ringing.

If he wants it to light up the room, he'll have to protect it when
ringing voltage is present on the line.

 50 years ago I designed the telco
circuits that detected when a customers wanted service.  It was a pain
to distinguish between a real off-hook from the customer and line
leakage due to poor cable insulation, squirrels, etc.

I had an old Automatic Electric phone containing a pot marked off in
terms of distance from the CO. I guess there were some long loops in
the rural areas served by the independent telcos who were Automatic
Electric's main customers.

Here's a picture of one of the "saltshaker" ringer lamps. Although
this one is stuck to the dial of a dialless phone:

http://wwwdelivery.superstock.com/WI/223/1598/PreviewComp/SuperStock_1598R-239648.jpg

 

[Robert Macy]

On Jun 17, 4:32 pm, vjp2...@at.BioStrategist.dot.dot.com wrote:

I want to put an LED to test my phone line, which I found to be ca 50v.

Where/how do I find the right LED?

THe LEDs at Radio Shack are all like 2v (yea I remember VCC of 2.3 on diodes
in my EE2 for non EEs course).

Should I just use a regular bulb, like the kind used for Christmas lights,
instead? (what about the LEDs used for CHristmas lights? Shouldn't they
work?)

Besides, I really only want ONE LED.

                                    - = -
 Vasos Panagiotopoulos, Columbia'81+, Reagan, Mozart, Pindus, BioStrategist
                   http://www.panix.com/~vjp2/vasos.htm
  ---{Nothing herein constitutes advice.  Everything fully disclaimed..}---
   [Homeland Security means private firearms not lazy obstructive guards]
 [Urb sprawl confounds terror] [Phooey on GUI: Windows for subprime Bimbos]

Your phone has three states
1. no power
2. OFF HOOK, well maybe ringtone coming in 90Vac at 20Hz ??
3. ON HOOK w/wo dial tone

you can make a simple little tester to catch all three states.

get two 2N5088 NPN transistors, two 10Meg, bridge rectifiers, 9v
battery, 10 r

 

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

- = -
Vasos Panagiotopoulos, Columbia'81+, Reagan, Mozart, Pindus, BioStrategist
http://www.panix.com/~vjp2/vasos.htm
---{Nothing herein constitutes advice. Everything fully disclaimed.}---
[Homeland Security means private firearms not lazy obstructive guards]
[Urb sprawl confounds terror] [Phooey on GUI: Windows for subprime Bimbos]

 

[Cydrome Leader]

vjp2.at@at.biostrategist.dot.dot.com 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.

 

[klem kedidelhopper]

On Jun 19, 1:27 pm, Cydrome Leader <prese...@MUNGEpanix.com> wrote:

vjp2...@at.biostrategist.dot.dot.com 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

 

[Robert Macy]

On Jun 20, 4:51 am, klem kedidelhopper <captainvideo462...@gmail.com>
wrote:

On Jun 19, 1:27 pm, Cydrome Leader <prese...@MUNGEpanix.com> wrote:





vjp2...@at.biostrategist.dot.dot.com 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.

 

Ok, I set up a 2p2t switch that turns off my in-home lines and instead goes to an
RJ11 jack. The telco says I should test this to see if the problem is mine or
theirs. SO far this is SOP.

So then me thinks, why should I have to scramble for a tel set to make a
test? Why not just put an LED there? So I need a 2700 ohn resistor in
series with the LED. I can still plug in the tel set, but the LED will tell
me immediately what is going on as soon as I swich from whole-house to
test-circuit.

- = -
Vasos Panagiotopoulos, Columbia'81+, Reagan, Mozart, Pindus, BioStrategist
http://www.panix.com/~vjp2/vasos.htm
---{Nothing herein constitutes advice. Everything fully disclaimed.}---
[Homeland Security means private firearms not lazy obstructive guards]
[Urb sprawl confounds terror] [Phooey on GUI: Windows for subprime Bimbos]

 

[hr(bob) hofmann@att.net]

On Jun 20, 2:30 pm, vjp2...@at.BioStrategist.dot.dot.com wrote:

Ok, I set up a 2p2t switch that turns off my in-home lines and instead goes to an
RJ11 jack. The telco says I should test this to see if the problem is mine or
theirs. SO far this is SOP.

So then me thinks, why should I have to scramble for a tel set to make a
test?  Why not just put an LED  there? So I need a 2700 ohn resistor in
series with the LED. I can still plug in the tel set, but the LED will tell
me immediately what is going on as soon as I swich from whole-house to
test-circuit.

                                    - = -
 Vasos Panagiotopoulos, Columbia'81+, Reagan, Mozart, Pindus, BioStrategist
                   http://www.panix.com/~vjp2/vasos.htm
  ---{Nothing herein constitutes advice.  Everything fully disclaimed..}---
   [Homeland Security means private firearms not lazy obstructive guards]
 [Urb sprawl confounds terror] [Phooey on GUI: Windows for subprime Bimbos]

It depends on what your problem is, you haven''t said if it is a noisy
line, no service at all, or WHAT IS YOUR PROBLEM you're trying to
fix. If you told us, you might get a good answerrr!!!!!

 

[Arfa Daily]

<vjp2.at@at.BioStrategist.dot.dot.com> wrote in message
news:jrt8d5$hmp$1@reader1.panix.com...

Ok, I set up a 2p2t switch that turns off my in-home lines and instead
goes to an
RJ11 jack. The telco says I should test this to see if the problem is mine
or
theirs. SO far this is SOP.

So then me thinks, why should I have to scramble for a tel set to make a
test? Why not just put an LED there? So I need a 2700 ohn resistor in
series with the LED. I can still plug in the tel set, but the LED will
tell
me immediately what is going on as soon as I swich from whole-house to
test-circuit.

- = -

You would still need to watch out for the AC ringtone, as this will try to
stick a huge reverse voltage across your LED on every half cycle. Your
resistor can be much higher than 2.7k with modern high efficiency LEDs. I
think I would go for around 10k as the series resistor, and also put a
1N4007 diode in inverse parallel with the LED. Of course, this only all
works at all, if your telephone operator doesn't use line polarity reversal
for line status signalling. It's been a lot of years since I learnt all this
stuff at college, but I seem to recall that this used to be the case - at
least here in the UK anyway - and was the reason that there was a bridge
rectifier in the telephone, so that the polarity inside remained the same,
irrespective of what was going on polarity-wise on the line. Perhaps Robert
would be more current on that.

Arfa

 

[Robert Macy]

On Jun 21, 6:05 pm, "Arfa Daily" <arfa.da...@ntlworld.com> wrote:

vjp2...@at.BioStrategist.dot.dot.com> wrote in message

news:jrt8d5$hmp$1@reader1.panix.com...

Ok, I set up a 2p2t switch that turns off my in-home lines and instead
goes to an
RJ11 jack. The telco says I should test this to see if the problem is mine
or
theirs. SO far this is SOP.

So then me thinks, why should I have to scramble for a tel set to make a
test?  Why not just put an LED  there? So I need a 2700 ohn resistor in
series with the LED. I can still plug in the tel set, but the LED will
tell
me immediately what is going on as soon as I swich from whole-house to
test-circuit.

    - = -

You would still need to watch out for the AC ringtone, as this will try to
stick a huge reverse voltage across your LED on every half cycle. Your
resistor can be much higher than 2.7k with modern high efficiency LEDs. I
think I would go for around 10k as the series resistor, and also put a
1N4007 diode in inverse parallel with the LED. Of course, this only all
works at all, if your telephone operator doesn't use line polarity reversal
for line status signalling. It's been a lot of years since I learnt all this
stuff at college, but I seem to recall that this used to be the case - at
least here in the UK anyway - and was the reason that there was a bridge
rectifier in the telephone, so that the polarity inside remained the same,
irrespective of what was going on polarity-wise on the line. Perhaps Robert
would be more current on that.

Arfa

Here in the US the telco sometimes would also do line reversal AFTER
you acquired the connection! Translates to Touch Tone Dialer didn't
work anymore! I haven't heard of it happening lately, but moot point,
every phone I've seen simply bridge rectifies and is done with it.

 

[spamtrap1888]

On Jun 21, 7:12 pm, Robert Macy <robert.a.m...@gmail.com> wrote:

On Jun 21, 6:05 pm, "Arfa Daily" <arfa.da...@ntlworld.com> wrote:









vjp2...@at.BioStrategist.dot.dot.com> wrote in message

news:jrt8d5$hmp$1@reader1.panix.com...

Ok, I set up a 2p2t switch that turns off my in-home lines and instead
goes to an
RJ11 jack. The telco says I should test this to see if the problem is mine
or
theirs. SO far this is SOP.

So then me thinks, why should I have to scramble for a tel set to make a
test?  Why not just put an LED  there? So I need a 2700 ohn resistor in
series with the LED. I can still plug in the tel set, but the LED will
tell
me immediately what is going on as soon as I swich from whole-house to
test-circuit.

    - = -

You would still need to watch out for the AC ringtone, as this will try to
stick a huge reverse voltage across your LED on every half cycle. Your
resistor can be much higher than 2.7k with modern high efficiency LEDs. I
think I would go for around 10k as the series resistor, and also put a
1N4007 diode in inverse parallel with the LED. Of course, this only all
works at all, if your telephone operator doesn't use line polarity reversal
for line status signalling. It's been a lot of years since I learnt all this
stuff at college, but I seem to recall that this used to be the case - at
least here in the UK anyway - and was the reason that there was a bridge
rectifier in the telephone, so that the polarity inside remained the same,
irrespective of what was going on polarity-wise on the line. Perhaps Robert
would be more current on that.


Here in the US the telco sometimes would also do line reversal AFTER
you acquired the connection!  Translates to Touch Tone Dialer didn't
work anymore!  I haven't heard of it happening lately, but moot point,
every phone I've seen simply bridge rectifies and is done with it.

My 1970s WECo phone will not generate dialing tones if tip and ring
are reversed -- no rectifier there.

When I worked for the telephone circuit company, two-party lines had
tuned ringers: 20 Hz for one party and 30Hz for the other. Is that
what line reversal was used for in the UK? to distinguish between
parties? Here you had to go to single party service if you wanted
touch tone dialing.

 

[Arfa Daily]

"spamtrap1888" <spamtrap1888@gmail.com> wrote in message
news:3c223bba-1cb2-4f62-b2c4-8cad9e928209@m2g2000pbv.googlegroups.com...

On Jun 21, 7:12 pm, Robert Macy <robert.a.m...@gmail.com> wrote:
On Jun 21, 6:05 pm, "Arfa Daily" <arfa.da...@ntlworld.com> wrote:









vjp2...@at.BioStrategist.dot.dot.com> wrote in message

news:jrt8d5$hmp$1@reader1.panix.com...

Ok, I set up a 2p2t switch that turns off my in-home lines and
instead
goes to an
RJ11 jack. The telco says I should test this to see if the problem is
mine
or
theirs. SO far this is SOP.

So then me thinks, why should I have to scramble for a tel set to
make a
test? Why not just put an LED there? So I need a 2700 ohn resistor
in
series with the LED. I can still plug in the tel set, but the LED
will
tell
me immediately what is going on as soon as I swich from whole-house
to
test-circuit.

- = -

You would still need to watch out for the AC ringtone, as this will try
to
stick a huge reverse voltage across your LED on every half cycle. Your
resistor can be much higher than 2.7k with modern high efficiency LEDs.
I
think I would go for around 10k as the series resistor, and also put a
1N4007 diode in inverse parallel with the LED. Of course, this only all
works at all, if your telephone operator doesn't use line polarity
reversal
for line status signalling. It's been a lot of years since I learnt all
this
stuff at college, but I seem to recall that this used to be the case -
at
least here in the UK anyway - and was the reason that there was a
bridge
rectifier in the telephone, so that the polarity inside remained the
same,
irrespective of what was going on polarity-wise on the line. Perhaps
Robert
would be more current on that.


Here in the US the telco sometimes would also do line reversal AFTER
you acquired the connection! Translates to Touch Tone Dialer didn't
work anymore! I haven't heard of it happening lately, but moot point,
every phone I've seen simply bridge rectifies and is done with it.

My 1970s WECo phone will not generate dialing tones if tip and ring
are reversed -- no rectifier there.

When I worked for the telephone circuit company, two-party lines had
tuned ringers: 20 Hz for one party and 30Hz for the other. Is that
what line reversal was used for in the UK? to distinguish between
parties? Here you had to go to single party service if you wanted
touch tone dialing.

I honestly can't remember why it was done. I never worked directly in phone
service provision, but back 40 years ago, college courses were 'well
rounded' affairs, and as well as the radio TV and electronics course that
was my primary module, we also had classes in math and telecom principles.
As an apprentice, I did a full 12 hour day at college, one day per week, for
five years ...

However, as Robert says, I seem to recall that the line reversal took place
after connection acquisition, and was for some kind of signalling purpose.
Maybe, it was used by other equipment in the chain to determine that the
line had been looped ?

I don't recall ever being taught anything about how party line routing
worked here, but it does seem as though that might be a valid way of using
line reversal signalling. There is an ex British Telecom engineer lives a
couple of doors up from me. He was an exchange engineer as far as I recall,
so I guess he should know the system backwards. Next time I see him out in
his garden, I'll ask.

Arfa