As Unions Mature An Analysis of the Evolution of American Unionism by Richard Allen Lester, FrederickH. Harbison Paperback, 182 Pages, Published 2011 by Literary Licensing, Llc ISBN-13: 978-1-258-21797-6, ISBN: 1-258-21797-X
"6.12 Block Diagram of Continuous-balance or Servo-balance DVM signal is a
function of the difference in magnitude and polarity of the d.c. voltages connected
to the opposite side of the chopper. ... The servo-motor also drives a drum-type
mechanical indicator that has the digits 0 to 9 imprinted about the periphery of its
drum segments. The position of the ... 1 ^J Servo \ Q i ^ / \ motor * , <_ Overload —
' ' i/ K X^^^^/ D v Input ..."