Temper: Carefully controlled heat treatment of the Invar rods to relieve stresses in the material. Only tempered Invar rods have predictable thermal expansion.

Torque: Turning force.

Transmission ratio: Determined by the number of teeth in a pair of engaging gears. Expressed as the number of turns the driven gear makes when the driving gear turns once.

Tungsten: Very heavy metal, density 19,3 g/cm3.

Temperature compensation:
The accuracy of a pendulum clock does not exclusively depend upon the mechanical properties of the mechanism, but also on external physical influences. The oscillation period of the pendulum is primarily determined by the pendulum length. Variations in temperature however result in a corresponding change of the pendulum length due to the linear expansion of the materials used. The pendulum rod of the Secunda Accurata 1958 consists of an iron nickel alloy, called super invar. This is characterised by an especially small linear expansion when temperature changes. In order to compensate for this residual expansion as well, the pendulum is equipped with a temperature compensation device. A small residual temperature error may however occur. It is therefore advisable to expose the clock only to small variations of temperature. If this is considered when the location of the clock is chosen, deviations of less than 1 sec. / month can be attained.

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