Greatest Holdies: I Hacked an Old Phone to Play the Greatest Hold Music.





Well... I'm pretty sure that you don't want a phone that just plays hold music...

But there are countless other exciting projects you can make with this very basic hack of these readily available "desk" phones.

Excited to see what other projects come out of this Instructable : )

Have fun!

Step 1: Parts Parts Parts


And of course, an old phone! For reasons I can't quite understand there are many cheap options for phones like this on Amazon. Who is buying them, and why? Here are some Amazon options:

Total cost for this project will be ~130$

Step 2: Check It Out

Open it up.

We can throw out the bell.

See that little white plastic lever on the circuitboard? That is what detects if the phone is hung up. We are going to use that because it is quite annoying to build our own switch for this.

Also note the color of the wires which connect to the handset speaker: red and green. (yellow and black are for the mic).

Step 3: Install Our 3W Speaker

In replace of the bell, glue in your 3W speaker.

I cut away the supports that were in the way.

Step 4: Intercept the Hangup Trigger

These are the points that we need to solder on the existing PCB to intercept the hangup switch. I connected my two green wires to them.

Don't worry if you have a slightly different phone. All phones will have a switch similar to this and you can use a multimeter tool to detect which pins go HIGH/LOW when the switch is pressed.

Step 5: Build the MP3 Shield

Great instructions on the Adafruit page for building your MP3 Shield:

Remember to close the 3pins that enable it to be used on an Arduino Mega.

And I also closed the pins that give it a +12db sound boost. It sounds like hell once these are closed, but whatever, this is hold music, right?

Step 6: Intercept the Keypad

Thankfully on my keypad the rows and columns were numbered on the circuitboard.

Sometimes keypads have 8 wires. Sometimes they have 7.

Make note of these numbers and what Arduino pins they are plugged into. You will need to enter this into the code later.

Step 7: Intercept the LED

Well, sadly, the LED on my phone was bust. But I am sure it works on other phones. Why not put it to use? You may want to add a resistor because I didn't see one on the tiny circuitboard the LED is mounted on.

Step 8: Install Our Proximity (Motion) Sensor

We use the proximity sensor to detect if someone is standing in front of the phone, and if so, it starts ringing. This is a great way to get people interacting with your phone without you being there. Who can resist an ambiguous bright red ringing phone? The answer is, no one.

Drill a hole carefully (start with a small bit and increase size). You can mount these ultrasonic rangefinders on the back side and even cover them up a bit and they will work just fine. I added a small acrylic piece for cosmetic purposes but if your drilling is good you shouldn't need it.

Step 9: Connect the Audio: Speaker and Handset

Left goes to the handset. Right goes to the speaker. Don't mix them up!

Step 10: Add the Tuning Dials

These are not essential but nice to have in case you want to tune some variables without having to re-upload the code every time.

I added two tuning dials. One for the distance (proximity) at which the phone is triggered.

The second is the duration before it starting ringing again after hung up.

Step 11: Get 'Em All in There

There is a very convenient screw hole that allows you to screw in the Arduino Mega right in between the speaker and the existing circuit board. It's like this phone wants to be hacked, right?

Also I spliced the power supply and soldered it directly to the Vin on the board. This saves space a bit.

Everything fits in there nicely.

Step 12: Upload the Code & Audio

The Arduino Code and MP3 files are attached.

Please read the Arduino code for instructions and comments.

Step 13: Finished!

Yay. You a Wizard Harry. Sail away sail away sail away...

Trash to Treasure

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Trash to Treasure



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    13 Discussions


    7 weeks ago

    Excelent! I have an old rotary phone. I had to boost the voltage to 40V to get the bell to ring and then kind of futzed around with it and left it half finished, but now I'm inspired to do something with it. I got discouraged b/c there's no room for the electronics inside that beast...


    2 months ago

    Very Nice, this object is amazing. I mean useless... but therefore amazing. Well done!


    3 months ago

    Hilarious! Thanks for sharing

    M. DwayneS

    3 months ago

    Great -ible, clever. Although, I have to admit I couldn't listen past about 1:30 mins into the video as I felt my life-force meter slowly ticking down.


    Question 3 months ago

    Just out of curiosity, can you still use this as a normal phone if you plug it into a phone cable?
    Sorry if it's a dumb question, I kind of just skimmed the text and I don't know much about arduino anyway xD

    2 answers

    Answer 3 months ago

    I believe it can still be used as a phone. Based on my scan of the 'ible, not much modification of the original circuit was done, and the only components removed or intercepted (bell, LED) are non-essential. I think it will still work.


    Reply 3 months ago

    Interesting. This sounds like an idea that could be taken in multiple different directions. Could just be a fun office desk piece, if it does still take calls, but I'm imagining changing the audio recordings and making it into some kind of prank involving "press this button for/if..." and a lot of "what the heck" from whoever is being pranked!


    3 months ago

    Nice! Neat that you can still find these for sale online - I'd make a mobile verison with a huge battery!
    It would also be great fun to make it play the hold music to the person
    calling, and have a button for a dumb, annoying song, in the case of
    telemarketers. *mental record player starts spinning ... "Never gonna
    give you up, ..." *


    Question 3 months ago

    This is so cool! I love it. Where do you get the small red acrylic piece that covers the motion sensor from?