It will work without it but it will work alot better with it. My old
Benmar CourseSetter autopilot didn't have a rudder position
sensor or any provision for one. They are now out of business.
Will Hamm of WH Autopilots said to me, "Now you know
why they are out of business". Rudder position feedback is
essential for a quality autopilot control. Spend the money, it
is worth it. Buy a cheaper galley stove instead.

Doug
s/v Callista

"Steve" wrote in message
...
It's a 5k ohm pot with the sensor arm on the wiper.. It's anolog but I
don't
know how the control unit deals with that..

I have been trying to get one on ebay.. They show up about once every week
or so and end up going for about $150 each.. The ones I have seen were new
or factory refurbished.

Your ST4000 will work without it, according to what I read in my ST5000
manual. You just have to note the absense in your configuration routine.

Steve
s/v Good Intentions