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Those remote controls are fairly simple in operation. You have two audio signal lines (L+R), a ground line, and a remote line. In order to put the player/recorder into different modes, you simply switch different resistances across the ground-remote line. So when you press the play button or the skip-track button etc on your remote control, you're simply switching different resistors onto the line.
I couldn't tell you what the resistance values are, but if you dismantle the remote it'd be pretty easy to find out for yourself.