This was contributed be the good doctor, Eaglion

TBFS001
 
As you can see the logic is rather simple. Each switch button momentarily 
creates a short circuit and signal to GNX3.
 
If lines of Ground and Middle connected > STOP/UNDO function (Corresponds to 
Switch A in FS300 and GNXFC)
 
If lines of Ground and Tip connected > RECORD function (Corresponds to Switch 
B in FS300 and GNXFC)
 
If lines of Ground,  Middle and Tip connected > PLAY function (Corresponds to 
Switch B in FS300 and GNXFC)
 
Read the part of the manual that describes FS300.
 
Installation:
 
As i leave in a hot and humid city the cables rust quickly. To repair a
rusted cable i have to unsolde 2/3 cables and resolder them back. So I
preffered to use a circuitboard and a female insert for 1/4 stereo jack
adaptor to avoid this so don't have to use a circuitboard (if you haven't
made one it can be hard to make it for the first time) and the insert. You
can direct solder the cables to switches.

Switches:

You need 2 switches which lets two lines contact at a time. These are
very easy to find. Just solder ground line to one end and tip or middle
to an other.

You need 1 switch with which lets three lines contact at a time. I couldn't
find a switch for three, all the switches in the market were either having
2 or 12 connection points. So i had to buy a 12 one. The problem was it was
also allowing the contact of only to lines at a time in regular action. So
I had to  make a few extra solderings to let three lines contact. The
trick for this is line should not be touching other before you push the
button. See switches diagram.

Becareful while soldering the switches a small flament of line or a small
piece of solder contacting to any other place will form a shortcircuit
enough for disfunction of the system.


There are several switches in the market prefer the button ones. They usually
don't come as trigger switches but as on/off switches which they stick in
and need to be pressed again to pop up. There is a small mechanism which
contains a mall staple like rod, under the spring of the button which
provides this.  If you remove this rod it will no longer sticks in and
acts like a trigger switch.


Dimensions of the box:

This is up to you. Enough height to keep the switches in and avoid them to
touch the ground or breake the circuitboard when you step on them. Put one
pair of your shoes next to each other. Measure the longest distance from
left outside to rightoutside. The width of the box should be a bit more
longer than this. If you place the middle switch in the center and the
others 3/4 inch from the sides you can press the middle button without
pressin others. Any depth that can keep all these in is enough. (I know
this sounded like Granma's Recipe)

Contributed by Eaglion