Retro Cell Handset Mod:
BELL SYSTEM PROPERTY
NOT FOR SALE
The Bell Model 500 desk phone manufactured for decades by Western Electric is an icon of
Twentieth Century product design. The evolution of the Model 500's receiver begun with
the first telephones produced in the late 19th Century and it's longevity has taken it into
the 21st. I have always found it to be ergonomically designed and comfortably to
use, It is the embodiment of "form follows function".
So when I saw the
SparkFun Rotary Cellphone I thought "Cool!, that was a great handset! but who wants to
carry the rest of it?" The gears kept grinding overnight, however, and the next morning
I awoke with a picture of the "BELL SYSTEM PROPERTY|NOT FOR SALE|WESTERN ELECTRIC cellphone
handset" in my head. Hmm, I think I've seen something like that before. $5.00 later (plus $8.00 for shipping) a
lovely black Model 500 was on it's way to me courtesy of America's Garage Sale.
Essentially I will take the plastic belt clip for my LG Vx6100 and embed it in the back of
the Western Electric receiver behind the ear piece. I'll then mount the active
components of a hands free headset in the receiver to make it fully functional.
Serendipitously, the voice command button for "driving mode" falls just under my thumb with
the cellphone mounted as such, with the phone in driving mode I'll be use voice commands to
dial. Unfortunately, the phone won't let me retrain "Contact" to "Operator get me . .
.", that would have been sweet!
First I took apart the headset and receiver. The wiring in the headset was easy to
figure out, there was a pair of lacquered wires for the ear piece and a tiny coax line for
the mic. I tested the Western Electric ear piece with the headset wiring harness and it
worked very well, it was clearer and much louder the the headset ear piece. Of course
the original carbon mic will not work so I will mount the electret mic from the headset in
the mouthpiece of the receiver.
Next I figured out about where I wanted to embed the cell phone belt clip. I used a
scribe to scratch an outline of the clip on the receiver. Next I completely spaced the
fact that I was taking pictures of the whole process in the hope of getting posted to
Slashdot. Nuts! there are no pictures of the cutting!
I used a Dremel tool and a hacksaw to section the back of the receiver. I was fairly
crude and did not worry about gaps unless they were more then a 1/4" or so. After
cutting away the back of the receiver I laid down bed of epoxy putty all around the edge of
the opening. I pressed the belt clip into place and let it harden for a couple of
minutes. I used FastSteel Epoxy putty but PIG putty or any of the many similar products
should work fine. Once the putty hardened up a bit, but before it was totally hard I
trimmed the excess with an Xacto knife.
I also packed some putty inside for added strength. Don't put too much in or it will interfere with the ear piece.
Next I mixed up some J-B Weld epoxy, the slow setting kind NOT the 5 minute kind. I put the epoxy in a syringe and carefully made a fillet that attached the belt clip to the receiver with a smooth transition. Don't use too much, it will run. Check it often while it cures, if you have a run or two you'll be able to trim it off with the Xacto knife.
Once everything was cured it is a simple matter to wire up the phone. I used black RTV to seal all but one of the little holes in the mouth piece. The electret that came with the headset turned out to be really cheesy so I replaced it with an element from this computer mic. The new mic sounds much better and the voice commands worked well after retraining for higher quality mic.
I stuffed the receiver with fiberglass to deaden an echo and prevent feedback, I also added a big nut to help the balance, it feels just right now.
I masked the assembly to paint the gray epoxy with Krylon High-Gloss Black.
The completed handset
Not only is it hands free, but the antenna is more then twice as far from my head reducing
my exposure to harmful cell phone rays by a factor of four!