air indexers?

hello;

please forgive the lack of capital letters and any typographical
errors. i am recoverying from left shoulder surgery and typing
one-handed.

while reading i came across two reference to "air indexers",
they were used before servos and steppers came in to use.
from what i able to find they operated off compressed air
and basically were somewhat like a stepper motor.

would anyone have any further information on these?

--
Terry L. Ridder
Blue Danube Software (Blaue Donau Software)
"We do not write software, we compose it."

For as long as I shall live
I will testify to love
I will be a witness in the
silences when words are not enough
With every breath I take
I will give thanks to GOD above
For as long as I shall live
I will testify to love
==Testify To Love==Avalon