#Old phone keypad how to#
#Old phone keypad code#
#Old phone keypad trial#

#Old phone keypad code#

The T9 was popularized with SMS texting on the first old compatible GSM phones (late 90s, early 2000), but today, with smartphones/iphones and their tactile interfaces and their complete keyboard, the T9 is disappearing but it can still be used to easily code secret messages. Then I can easily get on/off as digital values from the columns and rows and make sure the backlight works.The T9 patent is from 1985. What I’m going to do is remove the PCB and wire up everything on my own. I pulled apart the unit even more and discovered a Western Electric 557D is the brains of the operation, but it’s so old there doesn’t seem to be a datasheet online for it. This is precisely why I was hoping I could detect useful output from each of the row and column contact points. I don’t really care to get in the business of decoding these. I have a hunch the screw connections are responsible, at least in some part, for sending DTMF signals, also known as Touch-Tone. When that first row is high, I’ve attempted to also look for a high value from another row, but it triggers the wrong row too often.Įven making this short little video, which took at least 5 takes, there was a false trigger for pressing 1 and many key presses not being recognized. The values for the other rows fluctuate as expected. Well, the first row always reads a pretty high value, when a key on any row is pressed. I’m reading in analog values and using sampling along with standard deviations to determine which row’s value is unlike the others. Detecting the column of a button press was pretty straight forward and works great. I was able to get some code mostly working. It’s not surprising though, since this piece of technology is almost 40 years old! It would have made things so much easier. Unfortunately for me, the output from the contact points isn’t digital (limited to on/off), so I couldn’t use the Arduino library. There is probably something obvious I’m missing about how this all works together. With them connected this way, I don’t get the backlight, but I get data I can make sense of. When I connect them the opposite way, flopping to have 1 power and 4 grounds, the backlight on the keypad works, but the readings from the soldered contact points are useless. Something isn’t quite right about the screw connections though. I was using alligator clips on those, but disconnected them for the picture.

The other 3 screws also connect to power.

#Old phone keypad trial#

After some trial and error I determined which screws should be used for power (red wire) and ground (black) in order to get useable data out of the 7 switch contact points. I was in! From the way the keypad was connected to the rest of the phones circuitry I knew the screws were an important piece to tie it all back into the entire system. I figured out I could solder wires to the contacts points connected to each of those switches. Arduino has a Keypad library for working with modern keypads like one sold by Adafruit. This row/column grid system is still how we reference the individual keys on keypads like this. Then the left and right sides each have 2, which match up with the 4 rows of keys. The top has two and the bottom has one, which correspond to the 3 columns of keys on the grid. Eventually I realized what these contact switches on the sides were for.

#Old phone keypad how to#

It was a bit of a process figuring out how to tap into this thing. With the faceplate removed you can see the date stamp in the upper right. The part I thought would be neat to work with was this keypad.

I’m nowhere near that level, but you have to start somewhere right? I pulled the ringer, speaker, and microphone out of it. Perhaps the earliest and most well-known was the Steves (Jobs and Wozniak) using a blue box on payphones. People have been hacking phones for a long time. I didn’t take a picture before taking a screwdriver to it, but it looked exactly like the photo on the right. The previous owners left it in a storage room and I have no idea why I never pitched it. In addition to the switch I got a bunch of parts from, I’ve tore into a lamp and some old computer speakers. When I found an old telephone (it has a date of printed on it!) in my basement I knew I had to see what was inside. I’ve been on a kick tearing apart electronics.