I've had both the AH4000 wheel and this AH3000 tiller pilot apart and there
is no digital drive. Just a simple little 'weenie' motor and a set of
plastic reduction drive gears. (BTW the more recent, to 2000,
Autohelm/Ratheon APs still continued to use the same drive motors as the old
British Nautic and AH units.

I can put a meter on the motor leads from the control head and note the
switch of polarity from port to stbd.

The high freq. you maybe refering to could be from a pulse control to the
motor but from the circuit diagram of the control head, I can't see this as
'digital'.

You can download and look at the ciruit diagram on my web site..
http://hood.hctc.com/~esteve/private/manuals/ The document name is
AHcontrol head CCT1.doc


Steve
s/v Good Intentions