Some form of a motor or motor alternator is essential as a prime mover for the scanner and recorder machines. In most instances, means to provide synchronous power supply for the prime mover is required.
The following references illustrate how this problem can be solved.
Ranger (U.S. Patent 1,829,420, R.H. Ranger)
Karolus (U.S. Patent 1,856,076, A. Karolus)
Purrington (U.S. Patent 1,994,230, E.S. Purrington)
Cooley (U.S. Patent 2,015,742, A.G. Cooley)
Wolf (U.S. Patent 2,033,021, L.J. Wolf)
Adler (U.S. Patent 2,039,869B.Adler)
Young (U.S. Patent 2,117,587, C.J. Young)
(C) Marius Rensen