52 mm diameter.
The electronic operating hour counter is driven by a frequency-dependent stepping motor. The pulses needed for motor control are generated by a quartz-stabilized oscillator circuit, and processed by electronic circuitry. The oscillator is connected to quartz in a feed-back loop. The alternating voltage of the oscillator causes mechanical oscillation of the quartz, which generates a frequency to control the oscillation circuit. The oscillating frequency is necessary for the pulsing of the stepping motor.
The stepping motor rotation is transmitted to the number-wheel type counter and the operation indicator by a mechanical system.
The counter sums and displays the operating hours, the operation indicator displays the operation of the instrument in one-second steps. An indication wheel in the dial centre indicates that the operating hours counter is counting by turning in clockwise direction.