Hi,
I am new so first I wanted to say Hi to everybody.
I am a beginner and i would like to connect my mp3 between handset and phone of a landline phone.
The purpose is to play mp3 to play sound to the people I am in phone discussion with.
We still need to talk when the music is not playing.
For this purpose, in parallel, between handset and phone I would like to put a circuit.
But, how the circuit should be made ?
I saw many different circuit.
Any one can help ?

Thanks

 

Is this the same thread that is running on Electronics Point?

ak

 

Hi Analog kid.
Yes, it is.
Two points of view will maybe make things move faster
By the way, have you seen my reply ?
Which circuit are you talking about ? which one do you want me to modify ?

 

Is it impossible to connect an MP3 to a landline phone :-(
Come on, I am sure it is feasible.

 

You have two problems

1. AC couple the audio signal at the proper impedance
2. Avoid toasting your MP3 dur to the application of -48 VDC

Oh and the bandwidth is limited to a bit less than 3 kHz, so don't expect hi-fidelity sound reproduction.
It would also be good to figure out how to make the connction without the phone company knowing what you are doing. If they catch you it can result in some serious legal problems.

 

What you are describing is a lot like what used to be called a "phone patch". I don't know whether this ebay link will work, and if it doesn't you can go to ebay and search for "phone patch"
http://www.ebay.com/itm/Heathkit-HD...442?pt=LH_DefaultDomain_0&hash=item27f93c84a2

Here is a Google search that might help: http://lmgtfy.com/?q=phone+patch+circuit

In the United States one should use a registered Data Access Arrangement (DAA). I think this is a legal requirement. Cermetek has been making them for decades.
http://www.cermetek.com/Catalog/Telephone-Line-Interface/

 

I did this way back when, not hard at all.today you even have the interwebs for backup.

All you need is a little audio transformer and a cap. Radio Shack has the transformer (2573-1380) but the cap is more of a search: you need about 1 uf @250v non-polarized. RS has a cap with the right value but not the voltage rating, though it should work till the correct one comes in.

www.rane.com/note150.html or google"interfacing audio and pots"

 

What he is asking about is injecting headphone-level audio into the handset jack on a phone that normally expects an electret microphone element in the handset.

ak

 

There is two kinds of landline telephones. The POTS and the electronic ones. The electronic ones driven by integrated circuits being more likely your case are powered by the off-hook telco power around 6V.
Just connect your audio source very attenuated by a potentiometer in parallel to the handset cord pair that conveys its handset microphone pair and try adjusting the level.

This 'handset cord' is different than my earlier response in another site to inject/extract audio on the telco pair directly.

There is no 48V presence on a handset cord. There is no 48V presence on a off-hook telephone. The 48V are not allowed beyond the ringer circuit, by the hook switch. There is 48V at the telco pair only when on-hook.

Yes, it is perfectly possible to play your MP3 into a telephone conversation. But works by doing it, instead of typing into forums.