Connect MP3 to phone landline

Discussion in 'The Projects Forum' started by linningck1, Jul 6, 2015.

  1. linningck1

    Thread Starter New Member

    Jul 6, 2015
    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 ?

  2. AnalogKid

    Distinguished Member

    Aug 1, 2013
    Is this the same thread that is running on Electronics Point?

  3. linningck1

    Thread Starter New Member

    Jul 6, 2015
    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 ?
  4. linningck1

    Thread Starter New Member

    Jul 6, 2015
    Is it impossible to connect an MP3 to a landline phone :-(
    Come on, I am sure it is feasible.
  5. Papabravo


    Feb 24, 2006
    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.
  6. DickCappels


    Aug 21, 2008
    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"

    Here is a Google search that might help:

    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.
  7. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    I did this way back when, not hard at 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. or google"interfacing audio and pots"
  8. AnalogKid

    Distinguished Member

    Aug 1, 2013
    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.

    DickCappels likes this.
  9. Externet

    AAC Fanatic!

    Nov 29, 2005
    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.
    Last edited: Jul 13, 2015