Electricians/Engineers - strange switch

Factual Questions
1

I’ve got the front panel from an old Amana Touchmatic II microwave (Radarange, as they liked to call it). The buttons as I recall were heat-sensitive, only pressing them with your fingers would work, not a pencil eraser, or fork, or whatever item you had on you at the time. The buttons don’t move in at all, they’re just part of a solid glass plate. Each button has a conductive square on back which corresponds with a 2-pronged contact on the circuit board itself. The two prongs are connected about one third of the way up and have a common connection to the PCB. Several of the contacts appear to be connected via the PCB and several are independant of each other. The PCB consists of resistors, capacitors, some small transistors, a few LEDs, 18 of those strange contacts, and four ICs. The first IC has 16 pins and is labeled with two squiggly lines over each other, then - 839 and on the second line “DM7447AN”, as far as I can determine it is a fairchild LED controller. The second IC has 28 pins and is labeled “178204A-02” on the top line and just “ESSEX” on the second. The last two IC have 14 pin and are labeled “295 95 1” and on the second line “RCA 826”. I have pictures available, but no where to host them, and can take any picture that is needed.
Basically, I’m trying to turn this into the front panel for a computer case. Once I figure out how these switches actually work, the rest of the wiring won’t be an issue.

2

I’m pretty sure those ar capacitive switches. Basically, putting your finger on (or even only near) them changes the capacitance and triggers the circuit. the same principle is used in touch-screen applications, like some ATMs.

3

And some elevator buttons work this way in that they are heat sensitive.

4

Bet they’re capacitive.

Here’s a quick overview of the technology. Basically, they sense the parasitic capacitance of a plate. When your finger gets near the plate, the capacitance increases.

http://www.paia.com/touchsw.htm

Here’s a company that makes parasitic cap touch switch microchips that will work though up to 4 inches(!!) of glass!

http://www.qprox.com
I’m on another electronics project right now with some RF stuff, but when I’m done with that, I’m going to be playing with these touch sensors. They are ultra cool.
-Ben