I don't think there's an actual switch there, per se. Not like a CDL switch you'd add to an 80, or a rear defroster switch you'd have on a 62 or 4Runner.. or even the switches left of your steering column. Those switches in the center are more like the buttons on the front of your DVD player- they're just depressing something else on the back side, that's soldered to a circuit board.
at least that's my best guess, based on the 10-15x I've had mine in my lap futzing with the stereo.
82 fj40, 99 uzj100, 06 gx470
97 DR650, 05 525EXC, 01 XT225, 09 TTR125, 07 TTR90, 07 CRF50