Several years ago, when I was first getting into instructables, I was given a phone in use indicator light to go with my Plantronics headset and phone lifter combo at work. I hate it when people talk to me when I'm already on the phone, and I thought this would help, Sadly, the out of the box equipment was pretty dim, and not visible to everyone who might decide to strike up a conversation while I'm already having one.
With soldering iron in hand, I set about irrevocably altering company property without permission. I figured I knew enough about electronics to spice things up a bit. At the time I didn't think anyone else would find this idea useful, so I didn't take any process photos. Over the years, I've begun to notice just how many offices use these same headsets--they're everywhere! I don't think you'll have any problems though, this is a pretty straight forward operation.
Here is what you'll need to build one of your own:
A Plantronics wireless headset and indicator light
Some sort of IC socket (available at radioshack, online, or in your old and busted electronics)
LEDs of various sorts
Magnets (optional; I needed these to attach the board to the metal part of my divider wall, you may or may not need this)
First, crack open the case. On the front face of the circuit board are the five surface mount LEDs, sorry but no picture of them in place, you can see where they were in the pictures though. Carefully desolder and remove each one, making sure to keep the pads intact when you do. Once they are removed, attach a short (6-8 inch) length of speaker wire to each pad.
On a strip of perfboard, attach five IC sockets. Solder all the legs on each side of each socket together. Attach a speaker wire to each socket, the positive end of one side and the negative on the other. Now you will be able to drop an LED into each socket, the negative leg on one side and the positive on the other.
Glue some magnets to the bottom of the perfboard strip so it can attach to something metal (in my case, the top edge of the divider separating me from the front of the office). All done! At this point I spent a bunch of time collecting LEDs to be used in this device, from my already vast collection, from old electronics, and from LED Christmas lights.
The result was pretty awesome, and changeable to suit my whims. Most importantly it had 360 degrees of visibility. Still, it wasn't bright enough for my purposes, so I ended up giving it to my mom. I built an even grander version recently, and if you'd like to see a full instructable about it, follow/subscribe to me, I'll be posting it in the next couple of days (EDIT 6/20/11 -- full 'ible about my final in use light is live!).
Please take a moment to rate, subscribe, and comment! If you build your own version of this, make sure to post a picture in the comments below, I'll send you a digital patch and a three month pro membership!