32 January 2015
BUILD IT YOURSELF
By Joe Fox KD4MS
Panama City, FL
Over the years, I have seen many people on various forums asking if anyone has any
information on how to get an old IBM slave clock working as a time piece. A master
clock is required to control these old impulse secondary clocks (see Photo 1). These
impulse secondary clock movements — along with time attendance recorders, bells,
buzzers, etc. — were used for decades in
many schools, factories, and businesses for
coordinating time, so there are a lot of them
out there. Schematic 1 shows the basic
wiring of an IBM time control system that
was produced from about 1914 to
December 1958 in the US.
■ PHOTO 1. IBM master movement, spring driven.
■ SCHEMATIC 1. I. T.R. Service Instructions,
April 1, 1938, P16.