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Rotary phones are fun, the inginuity of the dial in combination with the phone centrals elektromechanical logic made it possible to allow telecommunications to evolve. These wonderfull devices are now disapearing from our desks (for many good reasons). But wouldn’t it be nice if you could still use a device like this to open up your webbrowser and visit your favorite website with just a single dial. Or perhaps dial a complete IP address and visit that. And ofcourse for some basic calculations you can also use your phone as an input device. Keep in mind that this project is a gadget, a gag, a joke. It should not be taken too serious. HOWEVER… it does work and it does so quite ellegantly!

Imagine this: You speak with a colleque about a specific website (that you have already bookmarked) and have a discussuion about it that requires you both to take a look at it. So you offer to open a webbrowser to take a look, then you do not touch the keyboard or mouse, but reach for the rotary dial phone that was hidden underneath a pile of paperwork. You clear it out, pick up the dial, hear the dialtone and dial a number, bweeeeieieirieirieireip noises come from the receiver and the website shows up on your screen. You act like this is completely normal and continue the discussion about the contents of the site. Then when you are done, you hang up the phone and the webbrowser is closed and you continue like nothing special happened. Leaving your colleague in complete confusion about what he/she just witnessed. Now how fun is that?

And all this isn’t that difficult to achieve, considering I already did all the work for your. So all you need to do is to find an old rotary dial phone with a single pushbutton , connect it to an Arduino pro micro with 2 resistors, 3 wires, an USB cable and perhaps a small case to neatly put it into.
How can this be achieved?
Below is the “schematic” of the internals of the phone and how the Arduino pro micro is connected.
As you can see, you only need 3 wires. The Blue wire is connected to the Arduino’s ground, the Green wire is connected to an IO-pin (used as input) via a resistor and by using internal pull-upps this line is now able to detect the pressing of the phone front button. The Red wire is connected to an IO-pin (used as input AND output) via a resistor and by using internal pull-upps this line is now able to detect the situation ON/OFF-hook and the dial pulses. The Red line is also used to apply a output signal, by quickly swithcing from input to output and modulating the output voltage between 0 and 5V and audible tone can be produced in the reciever. So with this simple circuit and some smart firmware we can detect on/off-hook, dial pulses, front button activity and make some sounds.

Unfortunately we cannot make the bell ring. This would require additional electronics as the ring-voltage is required to be much higher then 5V, but this is not a problem, because the project has no use for the bell anyway. In the beginning I thought it would be nice to make the bell ring when an email message was received, however, making that happen would be beyond the standard USB HID keyboard commandset. Meaning that it would require custom driver software to be loaded into the PC making the project instantly much more complicated.”

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