The other night instead of getting some sleep I found myself browsing for christmas gifts I would like to purchase this year. Naturally I made it too all my favorite hardware sites, but I soon found that I had already looked at that stuff before -- I wanted something **different**. I headed over to thinkgeek.com to get some ideas and after a few minutes of browsing I found it. A Retro Cellphone Handset. Sure, I have no idea what I would do with it, but it is such a sweet gadget for an oldschool phreak such as myself. As I looked at it, I realized they wanted $30+ for it, and I thought to myself -- I can build that. So after some cutting, testing, and building I have finished my Retro-Cell phone handset, and I will show you how you can build your own for under $10.00

Before you start, you need to take a look at your cell phone and identify how you would connect a headset to it. I have found by looking at several cell phones that most of the time this is accomplished by plugging in a 2.5mm Stereo Phone Jack (sometimes called 3/32"). You can double check your phone by comparing a standard headphone jack (like off your ipod) and verify that it is quite a bit smaller. A standard headphone jack is 3.5mm (1.8") I mention this step first, because it is very important that you get the correct phone plug before you heat up your iron.

After you have identified what type of phone plug you have on your cell phone you will need to assemble the following parts:

• Right Angle 2.5mm Phone Plug : Radio Shack Link : (or whatever size you need)
• Telephone Handset that you intend to use (see below)
• Assorted Hardware Hacking tools such as Wire Snips & Strippers, Soldering iron, Helping Hands, etc..

Identifying Our Target Handset

Getting the right handset is crucial to this build. The lucky thing is, the right handset means the right one for YOU. I will explore three different models of handsets, two that will work, and one that will not. The handsets that I will be referring to came off of these types of phones: Nortel Networks M3904 (think your typical modern office phone), a 1964 Western Electric Model 500 (think your typical old rotary telephone), and a Southwestern Bell Freedom phone with CallerID on the handset. Now I chose these specific phones because that is what I had access to. This is by no means a complete list of the handsets that will work with this project. Basically you are after a handset that is JUST a handset (as in, not a phone itself) and one that you like.

The two models that I have that WILL work with this project

Lets start out by discussing the Nortel Networks phone. This is just your standard modern office telephone. I chose it because it was easily accessible, and fit in my hand well. The benefit of using a modern phone, is that the handset will have a RJ-11 jack allowing you to disconnect the phone cord. You will see later that the older phones do not have this luxury. Along with the Registered Jack (trivia time) the newer phones use standard colored wires. We will be focusing our build on newer phones as the wires should be the same colors, and much more easily accessible.

Nortel Networks Handset

RJ-11 Jack on Telephone handset

Ok, so we saw our standard office phone, but what About the Western Electric Model 500? The oldschool phreak in me doesn't want to walk around with a brand new Nortel handset.. He likes the Model 500. Besides, who wants to feel like they are at work all the time? That is what I thought. The problem is, not everyone has a Western Electric Model 500 laying around that they want to destroy. (Again, make/model number is not important, just substitute any old rotary phone in its place) This is where your social hacking skills come in. (I threw the social "hacking" term in there just to piss off the haters on digg.com)

If you would like to find one cheaply, Start by combing your area. Visit the DAV, Goodwill, and other thrift stores. If you don't see anything, ask to look in the back. Tell them that you are looking for old phones, they don't even have to work. Most of the time they have a pile of old phones in the back that they think nobody wants. If that doesn't work, which btw it didn't for me, join your local freecycle (http://www.freecycle.org) group and ask for one there. This is the route that I went, and within 4 hours I had two generous offers for FREE phones. (I of course only took one, don't be greedy) If that still doesn't work, you can always hit ebay searching for terms like "Rotary Phone", "Vintage Phone", and "Retro Phone" trust me you will find several. The problem is these things are built like boat anchors, so shipping might get expensive.

Once you have your "Vintage Rotary Retro Phone" you will notice that the handset does not have any RJ-11 jack to disconnect it from the telephone. Oh well, we both know that you were going to take this thing apart anyway to get a good look at the insides... This just gives you a reason to do it sooner rather than later.

The insides of my Western Electric Model 500, notice the phone cord

As you can see, the phone cable will need to be cut out, and contains different colored wires than we are used to. (see image below) After I cut my handset away from my phone, I found that it has two white wires for the Speaker (use either for the ground),  along with a Red (Mic) and a Black (Mic Ground). If you intend on using an older phone, I suggest you take note of these, as I will not be discussing them later.

Model 500 Wires. Whites are Speaker leads, Red is Mic, and Black is Mic Ground

Lastly, lets discuss the Southwestern Bell Freedom Phone with Built in CallerID. During the late 80s phone manufacturing companies put out all kinds of these types of phones. Basically all the phone internals are in the handset, and the base is nothing but a base containing no (or very little) electronics inside. This type of phone will NOT work with this project, since the RJ-11 jack on the base of the handset is expecting a telephone connection, not a mic/speaker combination. Just a little FYI, if the handset contains any type of telephone guts, it probably is not going to work. Don't believe me? Fine go ahead and try it. These types of phones make great beige boxes (or DIY Lineman's Handsets), so if you have one don't throw it away just yet.

Ok, now that we have our handset picked out, lets interface it with our cell phone!

As I stated before, I will be using the Nortel phone for demonstration. I imagine most people will try this with modern phones, so I want the pictures and schematics to match the largest demographics. I gave enough information above for those of you with the older phones to figure out how to do it.

First you need to cut off one end of your phone cable. The end you want to cut is the end that would go into the PHONE --- Not the handset. Often the handsets use a smaller connector, so make sure you leave the phone cord plugged into the handset while you cut the other side.

After you have cut the RJ-11 off the phone cord, strip back quite a bit of the black shield. I suggest cutting back about 1-1.5", giving you enough room to work with. After you have your wire prepped, go ahead and get your mini-plug out, and start heating up your soldering iron.

Before we start we need to take a look at exactly how the mini-plug connector works. As you can see, it is separated out into three sections: The tip, middle and ground. Had you bought a mono plug, you would notice that it only contained two sections.. We need three.

Now that your soldering iron is warm, hold your wires to the plug. If you bought a right angle plug as I did, you will notice that the Mic wire (Red) will need to be a little bit longer than the Speaker wire (Yellow) which needs to be longer than the Ground wires (Green and Black). Trim the Green and Black wires giving you plenty of Yellow and Red left over to work with. Strip the ground (Green & Black) wires and solder them together, and then solder the pair to the ground section of your phone plug. Then trim and strip your Speaker wire (Yellow) and solder to the tip section, then finish off with the Mic wire (Red). See pictures below for clarification.

Once you put your phone connector shield on, your interface cable is complete. It should look very similar to the one below.

Now plug the RJ-11 end into your telephone handset, and the phone plug into the Headset jack of your cell phone. You should see that your cell phone immediately goes into headset mode. (Looks like I got some Text Messages and Voicemail to attend to)

As I plugged my Retro-Handset in, my phone went into Headset Mode

Now to test. Make sure you go out in public, Preferably a busy restaurant or the subway and pull out your totally retro handset and call your buddy up. Make idle chat while people around you stare in sheer jealousy.

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Ben D. submitted some of his pics. [In Use] [Connected]

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