(ET) E15 vs. E12 throttle control

[Chris Zach <cz alembic crystel com>]

So I am not too familiar with the various throttle controls since I 
normally use an E20. Anyway, this E15 wreck has a box of parts including 
what looks like a throttle. However it seems to only have 2 speeds 
forward and one reverse even though it has a complete set of switches.

Is there a difference between the throttles? Did different ones move 
different amounts, or is it just how the control harness handles the 
various switches?

Chris