The sony X1S looks just like an ir remote without the ir carrier signal. The pins are gnd, power and signal. As for the X2S, X3S, and X4S I believe they use a binary weighted resistance on each switch. For example 1k, 2k, 4k, 8k. Although I do not know the the values sony is using.

-Finally received my Mark2 no thanks to customs.
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Brian

-See my empeg <a href="www.hulkster.net/empeg" target="_blank">here</a>-