Telechron, Inc., Ashland, Massachusetts, USA. Model Type E, c. early
1930's, serial no. 17.
The genius of Henry Warren's design was his automatic frequency control mechanism. A
full explanation is featured in his patent #1906439. This covers an earlier design but it is
similar. Described briefly: A cam rotates once per period of the pendulum. This cam lifts
and lets drop a very small lever that imparts an impulse to the pendulum. If the cam,
which is driven from the frequency of the electrical line, is in full agreement with the
pendulum, which is assumed to be set correctly to a 1 second beat, the lever will contact
the pendulum at or very near the center of its swing which at that point imparts the
minimum of disturbance to its rate of oscillation. Through a complex system of levers the
movement can sense when and by how much the lever is out of phase with the pendulum. This
reading is then translated to a moving pointer that engages a set of curved contacts (see
diagram above). Depending upon where on the curve the pointer lands on either contact it
energizes a bi-directional motor to turn in either direction for an amount of time
depending on where the pointer touches the contact. The further toward the outside of each
curve, the longer the motor is energized which, through a planetary gear system will
advance or retard the cam to bring it into phase with the pendulum. If the cam, and
therefore the frequency of the line are in agreement with the pendulum, then the pointer
will be positioned between the two contact curves resulting in no electrical current to
the motor and no change in the output. This same motor is connected to the commutator that
translates these adjustments into electrical signals that can be reproduced by Mr.
Warren's patented motion reproducing motors. These
motors control the actuators that, in turn, control the mechanisms that mediate the rate
at which the generators in a power station will turn. This could be, for example, a sluice
gate in a hydraulic setting such as dam in the TVA (Tennessee Valley Authority) as was
probably the case where this clock came from, or to control a valve for the intake of
steam in a conventional coal or gas fired plant.
Photo from NAWCC Bulletin August 1991.