Telephone Questions

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Old 12-28-10, 01:10 PM
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Telephone Questions

What is the maximum voltage reached on a phone line?
 

Last edited by ray2047; 12-28-10 at 09:09 PM.
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Old 12-28-10, 03:17 PM
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Originally Posted by Justin Smith View Post
What is the maximum voltage reached on a phone line?
Most case 90 VAC @ 25 HZ but did see go high as 125 volts that is during the ring mode.

Merci.
Marc
 
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Old 12-28-10, 04:19 PM
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Could that damage the insides of a radio when ran into the "AUX IN" jack? (this may need to be a different thread)
 
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Old 12-28-10, 06:26 PM
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Originally Posted by Justin Smith View Post
Could that damage the insides of a radio when ran into the "AUX IN" jack? (this may need to be a different thread)
The AC is Ring voltage not talk or dial tone. And just to nit pick with Marc. Isn't that the frequency for a private line. Doesn't the frequency vary on a party line with each phone being set to a different ring frequency?

Since your interested in this Justin the original phones had large single cell batteries that powered a carbon microphone. A hand cranked generator in the phone provided the ring current.
 
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Old 12-28-10, 06:59 PM
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I figured out that if I soldered the red phone wire to the "LEFT" of a headphone jack and the green to the "COMMON" I could plug it into an audio source (headphone jack) and listen to music over the phone, but I am afraid to do so because of the high ringer voltage damaging a radio, ipod, mp3, etc. Will it cause harm?
 
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Old 12-28-10, 11:56 PM
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Originally Posted by ray2047 View Post
The AC is Ring voltage not talk or dial tone. And just to nit pick with Marc. Isn't that the frequency for a private line. Doesn't the frequency vary on a party line with each phone being set to a different ring frequency?

Since your interested in this Justin the original phones had large single cell batteries that powered a carbon microphone. A hand cranked generator in the phone provided the ring current.

Ray .,

To answer your question No it genrally don't change too much in USA side but once you get into international call it will varies a bit depending on the local phone or national phone set up.

The later techolgy do can change the ring frequinecty or type all it depending on the phone switch board can handle it or not.

For multi party line they can change the frequicey a bit or cycle of ring time one of the two.

On POTS system no it not really fiestiable but with later time it did add more convenice.

In France the tip and ring circuit is reversed what you have in the state.

But it run at 30 HZ during ring mode.

Merci.
Marc
 
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Old 12-29-10, 09:24 AM
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That probably won't work too well. Back in the day of the step by step or crossbar switch you could actually get decent fidelity over the phone line. I got near FM quality over a step switch. However now virtually all carriers will limit you to 4 KHz.

I would not connect the line directly for a variety of reasons. You can try a matching transformer but I don't know the specs offhand.

If you have an old POTS phone such as a Western Electric 2500, you could try removing the microphone from the handset and connecting the two contacts there to your audio output. I won't guarantee it won't blow it up, but I did that in the 70s to connect a Panasonic stereo to a WE 500 set. The "network" in the old phones will handle the mismatch without problems, but I can't say what would happen with a newer, less robust phone and audio device.

Another problem is that modern switches periodically test all the POTS lines and if they find induced voltages or something else out of spec, they will tag it. If repair finds something screwy on your line you may hear from them.

Matching transformers are always a good idea to isolate each side from the other, but there would be some loss involved.
 
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Old 12-30-10, 02:21 AM
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The street price of this interface is around $50. The info says, "Does not work with telephone systems" but that means it won't work with digital PBX (and VOIP) systems commonly found in offices. It will work well on a home POTS line.

As Arg said, the bandwidth is limited to around 4kHz, so don't expect hi-fi sound.
 
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