Touch-tone telephone puzzle

Hi all, I have a puzzle to build.

Description: A mp3 audio clue would be given through the handset if a sequence of numbers is dialed to a touch-tone telephone.

Now I have a vintage touch-tone telephone. Normally it connects to a phone jack but now I want to connect it to an Arduino nano. There are only 2 wires coming out of the cable as shown in the attached picture.

How would I build this puzzle?

phone.jpg

I think that trying to use the existing two wire connection is a non-starter.

You would need to simulate the telephone line that the two wires would normally connect to.
And then when you have done this you would just get audio tones when the keys are pressed.
You would then need a DTMF decoder to work out what keys were pressed.

I think you would be better off rewiring the telephone to bring out the keyboard row and column connections to the Arduino.

Can you clarify how you envisage the game working, please elginian?

Do you hear a pre-recorded mp3 audio clip, and then use the keypad to provide a response to what you heard, with the Arduino determining whether you are correct or not?

Hi JohnLincoln, I will store the pre-recorded audio file in a SD card memory shield and play it after the correct number is dialed.

  1. Once the handset is off-hook, the Arduino starts to read user's input.
  2. If the correct number is dialed, play the audio file stored in the SD card.
  3. Reset input number and stop playing audio when handset is on-hook.

These should be done without taking the telephone apart.

There is a tutorial on youtube showing how to do it with a pulse dial telephone with 3 wires.

Is this for an escape room?

EDIT:- Sorry, I wrote this without looking at the video.

Grumpy_Mike:
Is this for an escape room?

EDIT:- Sorry, I wrote this without looking at the video.

Yes, it is.

This circuit detects the dial tone from a telephone line and decodes the keypad pressed on the remote telephone.

http://www.electronics-diy.com/dtmf-decoder-using-mt8870.php

billhowl:
This circuit detects the dial tone from a telephone line and decodes the keypad pressed on the remote telephone.

I believe OP wants to do this without the actual telephone line in place. Which is a whole different proposition.

elginian:
These should be done without taking the telephone apart.

Now if you didn't have this requirement it'd be dead easy to do.