7x7 Day 5: Physical Exploration of An Old Telephone

So today my roommate gave me an old unused landline telephone and she said that I can play around with it. And so I did. I have never once in my life would think of 'butchering' unused gadgets just to see how the things inside actually worked, but I thought this might be interesting for one of my 7x7 projects.


With the help of this little multifunction blue tool (as pictured) which can transform itself to x-acto knife, screwdrivers, and even pliers, I tried opening up the telephone. Since it's pretty old, the screws attaching the outer interface to the circuit board inside was already rusted. It took me almost 2 hours just opening up the thing, which I finally succeeded using a saw. So here's what it looks like inside:

Since I didn't understand at all about the electronic components and how the landline telephone works, I started to educate myself online by browsing articles and watching DIY hacking projects. To help myself fully comprehend, I took a sketch of the basic component layout. My old red telephone has two main components called 'Base' & 'Headset'.

Base is consisted of:

  1. Switch/Plungers. It's the rectangular shaped thing that acts as an ON/OFF switch. When it's pressed, the main circuit will be closed, indicating that the phone line is not connected to the source.
  2. Main Circuit. When the plunger is not pressed, the main circuit will be opened and thus sends out an impulse that causes dial tone being played.
  3. Magnet, bumps around to create electromagnetic field to activate the ringer.
  4. Ringer, that acts as a signaling device. In modern telephones this is replaced by a speaker that plays different ringtones but in this case, I love the fact that it still uses traditional bell that produces familiar old-style ring.

On the other hand, Headset, has these things:

  1. Earpiece. Also known as internal receiver that is connected with coil to prevent feedback sound.
  2. Dialer, or Keypads. On the older telephone system this was replaced by rotary dial keypad, but in this case it's more modern so we no longer have to crank up the rotary to dial a number. There are 3 layers of Keypads: the Keypad itself, Keypad circuit board, and lastly is the main Headset circuit board.
  3. Mouthpiece, which basically is a microphone that acts as a transmitter to send your voice to the other line of receiving end.

Initially, I wanted to reuse the same old components and try making something new out of it. As far as I can tell, thing that is reusable enough was probably the Keypad. I was thinking that the Keypad can be connected to a Microcontroller/Arduino board/Raspberry Pi or even Bluetooth/USB port, and then become an input device that you can attach to some other things. So I started sketching the other possible form and I came up with these two ideas:

  1. Making a LED board game, or
  2. A Jukebox Player

My research took a really long time and after all, it was a dead-end. The challenge I faced was too big and too many to handle in such short period, like: "How do I connect the Keypad to the microcontrollers?", "Which wire cable connects to which part of this thing?", How do I program this thing to connect them to the LED board?", and so on.. and so on.

I know that is unfinished project, I realized that I'm running out of time and it's impossible to learn & implement all of this in 1 day. So hopefully when I'm armed with enough knowledge about physical computing I can continue on this left-over project.