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Jon
Guest
Mon Jan 23, 2012 8:20 am
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??
Guest
Mon Jan 23, 2012 10:02 am
On Mon, 23 Jan 2012 02:20:10 -0500, "Jon" <intrepid_at_bellaire.tv>
wrote:
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??
Telecom has pretty much always been positive ground, but phone lines
are balanced and should be floating so I'm not sure exactly what that
means when you're talking. Tip = negative and Ring = positive.
In some cases grounding one of those 2 lines will answer a call or get
a dial tone (or both ? Can't remember now)... That's how pay phones
partially used to work years ago. So, maybe one of the lines
were grounded and held the line ? I would think you would get
a very loud hum though by unbalancing the line like that.
They usual way to disconnect the phone line is to just open both
tip and ring (green and red) wires, usually.
boB
K7IQ
Phil Allison
Guest
Mon Jan 23, 2012 11:59 am
"Jon"
Quote:
What is the *correct* way to disconnect the phone service? Short the red,
the green or both?
** Unplugging the phone works real well.
Callers get a ringing tone.
Wot a jerk.....
.... Phil
Fred Bloggs
Guest
Mon Jan 23, 2012 5:18 pm
On Jan 23, 2:20 am, "Jon" <intre...@bellaire.tv> wrote:
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?
"Originally, the voltages on the wires were positive with respect to
earth. This is called negative ground, since the negative side of the
battery is grounded to earth. Then engineers discovered that with
positive voltage on the copper wires, copper wires age quickly, due to
electrolysis. With negative voltage on the wires, in respect to earth,
(called positive ground) the copper is protected from corrosion. This
is referred to as cathodic protection."
http://en.wikipedia.org/wiki/Tip_and_ring
Tim Wescott
Guest
Mon Jan 23, 2012 7:49 pm
On Mon, 23 Jan 2012 02:20:10 -0500, Jon wrote:
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??
Are you in North America?
Try Googling 'POTS line' (POTS = "Plain Old Telephone Service"). There's
lots - o - stuff there. POTS lines haven't changed much since the 1950s,
and you could probably make a 1920 phone work with minimal modifications.
The normal standard is for the lines to be a balanced pair, grounded at
the CO (or the local repeater), and positive ground (as noted). When
your phone is on hook (hung up) your house should present an open circuit
to the line. When your phone is off hook it should present a resistive
load of about 600 ohms to the line. If it's a normal residential POTS
line then you shouldn't connect one wire to anything other than the other
wire, and you really (by law) should only do that with an FCC approved
phone (although if you present it with something that looks like an FCC
approved phone to the wires, then things should work OK).
If you're having issues with the phone line, you should try calling the
phone company. Callers -- even machines -- who refuse to hang up is a
business problem, not a technological problem, and will probably fall to
a business solution before it falls to a technological one.
--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?
Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com
Don Y
Guest
Mon Jan 23, 2012 7:55 pm
Hi Jon,
On 1/23/2012 12:20 AM, Jon wrote:
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?
The phone operates at "-48VDC" (talk battery -- there really *is*
a "battery" in the CO -- a really BIG battery!). This helps reduce
corrosion in the wires (metal ions are drawn *to* the wire instead
of sucked away from it... an important issue if your company has lots
of money invested in *wire*!)
Ringing happens with 40-~130VAC (~90VAC nominal but depends on
how many REN's are hanging off the line -- all that wire has
some resistance to it!) applied to the pair.
Quote:
What is the *correct* way to disconnect the phone service? Short the
red, the green or both?
What do you mean by "disconnect"? The "on-hook" condition is signalled
by an "open" -- effectively no load (ring signal is capacitively
coupled to the ringer (and mechanical ringers were designed to
resonate at the ring frequency). When the phone goes "off-hook",
the CO (or SLIC96, etc.) senses the sudden load (~600 ohms) and
removes ring signal (loop-start) leaving talk battery (reverse
battery). When you "hang up", the CO will "acknowledge" this
by re-reversing or momentarily *dropping* battery.
[there have been different signaling schemes used over the years,
e.g., ground-start was a common trick with payphones...]
If you want to *look* like your phone is "in use", put ~600 ohms
across the pair. If you want to look like your phone is disconnected,
DISCONNECT IT! (Gee, clever idea, that!)
[A heap "old button" can be fabricated out of an LED and bias network]
There are ways to remain connected yet present an even smaller profile.
Quote:
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??
You really don't want to short the pair. Nor let it reference earth,
etc. TPC routinely checks lines for trouble and may elect (automated)
to pt your line out of service if it finds such a problem. Perhaps
even dispatching a service call (if the trouble is found to be *yours*,
you might end up with the bill)
What are you trying to accomplish?
FWIW, google "BORSCHT" and start there.
Howard Eisenhauer
Guest
Tue Jan 24, 2012 1:57 am
On Mon, 23 Jan 2012 07:18:58 -0800 (PST), Fred Bloggs
<bloggs.fredbloggs.fred_at_gmail.com> wrote:
Quote:
On Jan 23, 2:20 am, "Jon" <intre...@bellaire.tv> wrote:
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?
"Originally, the voltages on the wires were positive with respect to
earth. This is called negative ground, since the negative side of the
battery is grounded to earth. Then engineers discovered that with
positive voltage on the copper wires, copper wires age quickly, due to
electrolysis. With negative voltage on the wires, in respect to earth,
(called positive ground) the copper is protected from corrosion. This
is referred to as cathodic protection."
http://en.wikipedia.org/wiki/Tip_and_ring
Yon article has a few problems-
The reason they went to negative ground was in the days of single wire
circuits using a ground return path they ran into corrosion problems
with the ustomer end ground rods. Going around replacing these was
getting costly so they reversed the loop votage moving the issue to
the CO end, which then became a simple routine maintenance issue.
Going to a loop system eleiminated the issue pretty much entirely with
only a few special circuits such as PBX lines using ground path
returns anymore.
(& the statement that T1's are polarity sensitve is incorrect too)
H.
PeterD
Guest
Tue Jan 24, 2012 1:18 pm
On 1/23/2012 2:20 AM, Jon wrote:
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??
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.
--
I'm never going to grow up.
Robert Macy
Guest
Tue Jan 24, 2012 5:55 pm
On Jan 23, 2:02 am, boB wrote:
Quote:
On Mon, 23 Jan 2012 02:20:10 -0500, "Jon" <intre...@bellaire.tv
wrote:
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??
Telecom has pretty much always been positive ground, but phone lines
are balanced and should be floating so I'm not sure exactly what that
means when you're talking. Tip = negative and Ring = positive.
In some cases grounding one of those 2 lines will answer a call or get
a dial tone (or both ? Can't remember now)... That's how pay phones
partially used to work years ago. So, maybe one of the lines
were grounded and held the line ? I would think you would get
a very loud hum though by unbalancing the line like that.
They usual way to disconnect the phone line is to just open both
tip and ring (green and red) wires, usually.
boB
K7IQ
shorting the wires should look like "OFF HOOK" and after the sequence
of the phone company saying phone is off and beeping at you [which you
can't hear since the wires are shorted] the phone company disconnects
you from their network. Then, I don't know if the line appears BUSY
or simply RINGS to an incoming call.
Robert Macy
Guest
Tue Jan 24, 2012 6:01 pm
On Jan 23, 11:49 am, Tim Wescott <t...@seemywebsite.com> wrote:
Quote:
On Mon, 23 Jan 2012 02:20:10 -0500, Jon wrote:
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??
Are you in North America?
Try Googling 'POTS line' (POTS = "Plain Old Telephone Service"). There's
lots - o - stuff there. POTS lines haven't changed much since the 1950s,
and you could probably make a 1920 phone work with minimal modifications.
The normal standard is for the lines to be a balanced pair, grounded at
the CO (or the local repeater), and positive ground (as noted). When
your phone is on hook (hung up) your house should present an open circuit
to the line. When your phone is off hook it should present a resistive
load of about 600 ohms to the line. If it's a normal residential POTS
line then you shouldn't connect one wire to anything other than the other
wire, and you really (by law) should only do that with an FCC approved
phone (although if you present it with something that looks like an FCC
approved phone to the wires, then things should work OK).
If you're having issues with the phone line, you should try calling the
phone company. Callers -- even machines -- who refuse to hang up is a
business problem, not a technological problem, and will probably fall to
a business solution before it falls to a technological one.
--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?
Tim Wescott, Communications, Control, Circuits &
Softwarehttp://www.wescottdesign.com
OFF HOOK is more like 100 to 120 ohms DC resistance and indeed is 600
ohm AC resistance.
And the phone compnay switches between the power supply that senses
whether your phone is ON/OFF HOOK to another different supply that is
used for conversations. You can actually see athe voltage drop to zero
during that transition.
For operating ranges, like open circuit means leakage currents less
than ?? uA [I know 1 uA is allowed.] see the IEEE spec, used to be
FCC Part 68, but now it's an IEEE spec. There are all kinds of min/
max operating ranges listed in the spec.
Guest
Tue Jan 24, 2012 8:21 pm
On Tue, 24 Jan 2012 07:18:31 -0500, PeterD <peter2_at_hipson.net> wrote:
Quote:
On 1/23/2012 2:20 AM, Jon wrote:
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??
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.
I didn't know that any phone systems still did that. One reason for
polarity reversal was for billing purposes. Depending on the old
switching system, #1 crossbar, #5 crossbar, step, etc., the
reversal would be for just a moment or for the whole call and
sometimes not at all to the end user.
My experience with phone systems was from many many years ago and a
lot has changed sine the 60s and 70s. But the loop from the CO to the
end user is pretty much the same.
If your area has a telephone museum, I highly reccomend going to see
it. Seattle has a very nice one called the communications museum now
thatat least used to be run bypeople from the telephone pioneers of
america and has #1, #5 crossbar, ESS, AND Panel all talking to each
other as well as many more very cool exhibits. The volunteers can
easily answer most of these questions too.
http://museumofcommunications.org/
boB
Jon
Guest
Wed Jan 25, 2012 6:48 am
I'm not unplugging all 5 phones in the place every time I want no ringing.
Wot a jerk
"Phil Allison" wrote in message news:9o4ssaFle0U1_at_mid.individual.net...
"Jon"
Quote:
What is the *correct* way to disconnect the phone service? Short the red,
the green or both?
** Unplugging the phone works real well.
Callers get a ringing tone.
Wot a jerk.....
.... Phil
Guest
Wed Jan 25, 2012 7:27 am
On Wed, 25 Jan 2012 00:48:57 -0500, "Jon" <intrepid_at_bellaire.tv>
wrote:
Quote:
I'm not unplugging all 5 phones in the place every time I want no ringing.
Wot a jerk
"Phil Allison" wrote in message news:9o4ssaFle0U1_at_mid.individual.net...
"Jon"
What is the *correct* way to disconnect the phone service? Short the red,
the green or both?
** Unplugging the phone works real well.
Callers get a ringing tone.
Wot a jerk.....
... Phil
How about disabling the ringer in most or all of the phones ?
Phil Allison
Guest
Wed Jan 25, 2012 7:32 am
"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
Wed Jan 25, 2012 5:38 pm
"Jon" <intrepid_at_bellaire.tv> wrote in message
news:RMidndrj6JdfCoLSnZ2dnUVZ_sudnZ2d_at_earthlink.com...
<snip>
Quote:
"Jon"
What is the *correct* way to disconnect the phone service? Short the
red, the green or both?
snip
How about changing that switch in your control box to a DPDT center off
type. That will provide you a way to cut off all phones from one location.
--- Posted via
news://freenews.netfront.net/ - Complaints to news_at_netfront.net ---
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