old phone keypad


I got a 4x3 keypad from an old phone. On the PCB it says 'NS-E002' but I couldn't find its data sheet. It has 8 interface pins which i don't know the far left or far right one is pin 1.

(see image below)

Sorry I can't post an image. If anyone is willing to look at it please let me know I will send you a mail.


generally, pad one is a square joint where it is connected, where as the rest are round. Said that, I'm not sure when they started that!

Can you just hookup a multimeter and test connections?

~Kam (^8*

Hi Kam,

I've got a multimeter now. Can you please tell me how to check it?

Will I be able to use this 1 x 10 keypad the same way?


Setup your multimeter to make a tone when both leads make a connection.

Once you get that, press one of the keys, put one line of the multimeter on one of the pins, and the other line onto the next, keep testing pins until you make a tone. Once you get the tone, you know that that pin when high if for that key. Continue until you id all the pins. You'll notice a pattern.

For example, my 10 key (looks just like a touch tone phone) has 7 pins. Putting the meter on pin #1 and pin #7 is for the "1" key, pin #2 and pin#7 is the "2", etc

1-7 = 1 2-7 = 2 3-7 = 3 1-6 = 4 2-6 = 5 3-6 = 6 1-5 = 7 2-5 = 8 3-5 = 9 1-4 = * 2-4 = 0 3-4 = #

Make sense? All you're doing is making a connection with the meter.

About the other question using the ROTARY dial, I really don't know. I would assume that it gives "ticks" (high?) for each "tick/click" of the dial...maybe you have to count the "ticks"?

If you find out, let me/us know, what a fun input device...

~Kam (^8*

I was thinking about using it to make a Bluetooth hands free, but it takes three hands to operate. :)

Sorry I diverted your thread but it made me think how much HIDs have changed.

Y'know, EJ, you could probably enhance the protection offered by an an alarm system by using a dial: these days, half the amateur burglars-of-opportunity wouldn't even recognize it as the input device ;D

LOL, that’s a great idea!

The pizza guy can’t operate the keypad on the front of my building half the time either. I can picture a potential burglar scratching his head. Too funny!

Sorry I can't post an image.

You can't on your first post. Now that you're up to 3, you should be able to.

On the off chance that anyone actually cares... :)

The dial switch on a rotary phone is in series with the hookswitch. As the dial spins back to its normal position, it rapidly opens and closes the switch. So, in theory, if you were really fast and well-coordinated, you could "dial" a phone by rapidly twiddling the hookswitch.

There's an excruciatingly-detailed description of the operation here.


So, in theory, if you were really fast and well-coordinated, you could "dial" a phone by rapidly twiddling the hookswitch.

Yes it did work. I remember trying that way back in the 50s when we first got a phone.

Ten years later I hooked up a rotary phone dial to a binary counter (made from transistors as ICs hadn't been invented) with flash light bulbs as an output to make an "electronic adder", input in decimal output in binary.

My uncle used to put a lock on the phone, the kind that stops the rotary from spinning, but we used to just tap the hookswitch to dialout! he never figured out how we used to do it! ;D

We actually have a functioning "old" phone at home, and when my daughters friends come over (13 y/o), most of them have no idea how to dial it... funny stuff.

~Kam (^8*

That's a picture of my landline phone. It is a 1930's "candlestick".

Maybe you could hook it to an Arduino and a HT9200 Holtek DTMF Generator and get Touch Tone! :) http://www.futurlec.com/ICSFOthers.shtml

Yeah, but then the phone company would want to charge me for tone dialing. :(

Cool idea though.

It's likely that wouldn't charge you: the days when they plugged your pair into different frames depending on whether you paid for touchtone are long gone.

Of course, we've also passed through the period when it was fairly safe to cheat, because you're probably on a switch with enough smarts to keep track of who's paying...

If you want an autodialer, one approach that would be fun would be use a servo with a protruding "finger" to spin the dial. You'd need to do a little gearing to get the full 330-or-so degrees of motion needed if you used a standard RC servo. Or maybe use one of the ones that's been modified for continuous motion, and add an encoder to determine how far it's rotated.

Or, for real special-effects magic, if you can find another phone at a flea market or yard sale, gut it and put mechanics inside so it appears to be picking up and dialing itself.


That gives me some ideas. The candlestick phone base is very thin, the ringer is in a separate wall-mount box, so there is not much room for a servo motor, but a slightly later model, one could do some fun things inside.

I've got a servo project I'm working on now where I'm getting some large pointer hands and 3D numerals laser cut to make an "analog" thermometer and RH indicator. The readout is analog but everything else is digital.

Yeah, but then the phone company would want to charge me for tone dialing

I honestly didn't know there was anywhere left (in the US at least) that you could actually use a pulse phone!

I use my 40's dial/pulse phone here in Santa Cruz just fine! Never had an issue. Still works just fine.

When I got it, it would not work, so I took a pic of the inside, and posted it online, and within 20(?) minutes, I got a complete wiring diagram from an old timer AT&T phone tech. Got to love it!

~Kam (^8*