Old rotary phone - play music and dial detection

Other Hardware Audio
1

Hi, newbie says hello.

I'm trying to connect old rotary dial telephone to arduino - so that user could dial a number and then mp3 file would be played in a phone's speaker. I'm working on UNO and http://www.elecfreaks.com/wiki/index.php?title=Freaduino_MP3_Music_Shield . Phone has only one pair of cables - used for dialing and transmitting audio to speaker.

So far I've done dial decoding (treating phone as a switch) - I'm counting breaks in a phone circuit, it works correct. Now I'd like to connect it to MusicShield's line out - but can't really do that, because I would have to connect to line-out same wires that I'm already using for dial detection (I'd guess it's gonna cause a short - is it?).

So - the question is: how can I play music and detecting dialing in the same time? Is it maybe possible to get a MusicShield to detect jack connection?

2

You AC couple the audio signal into the wires. That is you connect them through capacitors so that you don't short things out.

3

'm trying to connect old rotary dial telephone to arduino - so that user could dial a number and then mp3 file would be played in a phone's speaker. I'm working on UNO and Welcome to ELECFREAKS WIKI — ELECFREAKS WIKI . Phone has only one pair of cables - used for dialing and transmitting audio to speaker.

A standard RJ11 phone jack and phone cable has 4 wires (for the option of 2 phone lines). Your old rotary phone may not have have an RJ11 jack, but 4-conductor phone cable is standard.

Since this is a custom project, it seems you could use a multi-conductor cable with as many wires as you want! Or, build the whole project inside the phone...

At least you don't have to deal with the ringer voltage!

You AC couple the audio signal into the wires. That is you connect them through capacitors so that you don't short things out.

You are still going to short-out the audio signal when you dial. You'd need a resistor for current limiting so you don't kill the amplifier.

Now I'd like to connect it to MusicShield's line out -

I don't know the impedance of the "speaker" in a telephone telephone. But, you can't drive a normal 8-Ohm speaker with a line-level signal. I also don't know the specs for the Music Shield, but typically a line-out would be connected a line input with an impedance of 10K or more.