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miso
Guest
Fri Jan 27, 2012 7:45 am
Quote:
One must also consider that when a phone goes 'off-hook' the exchange
may reverse the polarity. This is done around here (not sure of the
historical reason) with the telephone system.
My recollection from dealing with system houses that design line powered
gear is that you never trust the polarity of a phone line. They add a
diode bridge to get the proper polarity.
OK, this is EDN, but still, I believe this is the general scheme for
line powered design.
>
http://www.edn.com/article/461011-Get_power_from_a_telephone_line_without_disturbing_it.php
Bob La Londe
Guest
Wed Feb 01, 2012 8:01 pm
"Jon" <intrepid_at_bellaire.tv> wrote in message
news:s8Wdnae8qp25l4DSnZ2dnUVZ_rKdnZ2d_at_earthlink.com...
Quote:
I checked the dc voltage on my phone line. The green is +48vdc and the
red is ground. In my circuit I disconnect the phone line by disconnecting
the green wire because it has positive voltage on it. What is going on
here? Why is the green wire positive and the red wire negative? Is +48v
the dc equivalent to an ac voltage? If so why is it biased so much to
+48vdc?
What is the *correct* way to disconnect the phone service? Short the red,
the green or both?
btw, shorting the green wire effectively disconnects the phone service ok,
even if it is the wrong wire to short. When people try to call me all
they get is a constant ringing, and I hear nothing. In one case an
automated message from the pharmacy wouldn't disconnect no matter what.
The message kept going even on only one wire. How did that happen??
Tip - Green - wh/blu
Ring - Red - blu/wh
Ground - (Usually not used internally today)
There are a number of ways that other conductors could be used.
Ground start and loop start are two different ways to indicate you want a
dial tone. Most modern COs provide primarily loop start circuits.
Usually ring voltage is about 20hz and around 90-100 volts AC. Most
commonly this is over the same pair of wires as the voice, and dc power.
However at one time two party party lines where common and they would send
the ring voltage from tip to ground for one party and from ring to ground
for the other party. This was a quick and dirty way to provide more phone
services than they had pairs in the field.
Regarding party lines, another way it was done was to send different
frequency ring power over the talk pair. This required multiple ring
frequency generators in the CO, but were often implemented to provide
service to upto 4 different parties on a party line. They had telco
provided phones with ringers designed to ring at only a specific frequency.
I have heard that some services attempted to implement ground ringing and
multiple frequency ringing for upto 8 party lines, but that it did not work
very well.
Most modern residential telephones are loop start and have "line voltage"
ringers. They will ring at any frequency ring voltage received.
If you were on a party line in the past you were not allowed to provide your
own telephone equipment. With modern analog and digital carriers capable of
providing multiple true lines of service over limited pairs of wires I am
not sure if there are many (if any) places where party lines are still in
use.
Bob La Londe
Guest
Thu Feb 02, 2012 6:35 pm
"Bob La Londe" <none_at_none.com> wrote in message
news:l_fWq.5574$wR2.1117_at_newsfe01.iad...
Quote:
"Jon" <intrepid_at_bellaire.tv> wrote in message
news:s8Wdnae8qp25l4DSnZ2dnUVZ_rKdnZ2d_at_earthlink.com...
I checked the dc voltage on my phone line. The green is +48vdc and the
red is ground. In my circuit I disconnect the phone line by
disconnecting the green wire because it has positive voltage on it. What
is going on here? Why is the green wire positive and the red wire
negative? Is +48v the dc equivalent to an ac voltage? If so why is it
biased so much to +48vdc?
What is the *correct* way to disconnect the phone service? Short the
red, the green or both?
btw, shorting the green wire effectively disconnects the phone service
ok, even if it is the wrong wire to short. When people try to call me
all they get is a constant ringing, and I hear nothing. In one case an
automated message from the pharmacy wouldn't disconnect no matter what.
The message kept going even on only one wire. How did that happen??
Tip - Green - wh/blu
Ring - Red - blu/wh
Ground - (Usually not used internally today)
There are a number of ways that other conductors could be used.
Ground start and loop start are two different ways to indicate you want a
dial tone. Most modern COs provide primarily loop start circuits.
Usually ring voltage is about 20hz and around 90-100 volts AC. Most
commonly this is over the same pair of wires as the voice, and dc power.
However at one time two party party lines where common and they would send
the ring voltage from tip to ground for one party and from ring to ground
for the other party. This was a quick and dirty way to provide more phone
services than they had pairs in the field.
Regarding party lines, another way it was done was to send different
frequency ring power over the talk pair. This required multiple ring
frequency generators in the CO, but were often implemented to provide
service to upto 4 different parties on a party line. They had telco
provided phones with ringers designed to ring at only a specific
frequency. I have heard that some services attempted to implement ground
ringing and multiple frequency ringing for upto 8 party lines, but that it
did not work very well.
Most modern residential telephones are loop start and have "line voltage"
ringers. They will ring at any frequency ring voltage received.
If you were on a party line in the past you were not allowed to provide
your own telephone equipment. With modern analog and digital carriers
capable of providing multiple true lines of service over limited pairs of
wires I am not sure if there are many (if any) places where party lines
are still in use.
I might add a short to ground may or may not cause the phone line to fail.
Usually in normal circumstances a short to ground is due to a defect, is
typically higher resistance, and causes loud obnoxious noise on the line.
Similar, but not the same as an imbalance from one of the pair being broken
in the field. A good phone man can hear the problem and identify it from
the sound usually. Then its just a matter of determining the distance to
the fault. A dead short on the line between the pairs is interpreted as a
busy and will time out eventually. It may even be disconnected at the CO.
It will depend on the CO and the actual management practices of the
personnel there. An open an open on one conductor will simply not connect
to the site. A call will ring until they give up or in some cases times out
after so many rings (due to black box prevention timing).
Why not just buy a phone with a selectable ringer and turn off the ringer.
Jon
Guest
Sat Feb 04, 2012 11:03 pm
Phil the Jerkoff is a fucking jerk. Maybe he needs a phone stuck up his
stinking ass
"Phil Allison" wrote in message news:9o9lvvFfk8U1_at_mid.individual.net...
"Jon the Jerkoff "
Quote:
I'm not unplugging all 5 phones in the place every time I want no ringing.
** You have FIVE phones on the same line ??
Wot a fucking jerk !!!!!!!!!!!
Jon
Guest
Sat Feb 04, 2012 11:11 pm
Phil got a call from last night's supper
"Why did you eat me?"
"You were food, fucking jerk."
"Then UNeat me. Barf me out, bigot! Stick me back up there and barf me
out. I was a happy carrot at one time until you came along. Do you ever
consider that vegetables and ground beef have feelings?"
"Jon" wrote in message
news:AYqdnQmdhOSNNrDSnZ2dnUVZ_t6dnZ2d_at_earthlink.com...
Phil the Jerkoff is a fucking jerk. Maybe he needs a phone stuck up his
stinking ass
"Phil Allison" wrote in message news:9o9lvvFfk8U1_at_mid.individual.net...
"Jon the Jerkoff "
Quote:
I'm not unplugging all 5 phones in the place every time I want no ringing.
** You have FIVE phones on the same line ??
Wot a fucking jerk !!!!!!!!!!!
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