"The Enlightenment" wrote in message ...

Its sounds crude but was quite accurate. A full serve system would
involved resistors for position sensing that were amplified in DC,
amplidynes which operated in AC to generate mathematical functions
such as sine, cos etc (amplidyne is a sort of rotary transformer in
which the overlap of the poles of the two secondary windings are
added/subtracted from each other. The area of he poles can be used to
generate voltages that are functions of shaft position.

By the way, I think you are confusing "Amplidyne" with "Synchro" and
"Selsyn". An Amplidyne is a special motor-generator that basically
acts like a magnetic amplifier - vary the fields a little and get a
larger change on the output. A Synchro (or Selsyn) is what you mean -
a rotary transformer that can transmit angular data electrically
(generally with three wires as multiphase AC). The things that can
generate the sine and cosine from an angular shaft position are called
"Synchro Resolvers".

William Donzelli