Metronome

Metronome, a device that marks time through regular intervals (within the range of 40 to 200 beats per minute); it consists of a spring clock mechanism that drives a pendulum, each swing of which is accompanied by a tapping sound. The frequency of the metronome's beats depends on the position of a small movable weight on the pendulum rod, which extends significantly above the axis of rotation. Numbers on the scale opposite the upper end of the weight indicate the number of beats per minute. The metronome is used in physiology for timekeeping, as well as a periodic circuit breaker and closer, for which a metal wire with bent-down ends is attached to the pendulum rod. As the pendulum swings, the wire ends alternately dip into mercury cups, which are connected to a current source and to the place of its application (for example, a nerve, muscle, electromagnetic time marker, etc.). The metronome is also used as a sound stimulus for developing conditioned reflexes (see), for which it is equipped with a pneumatic device for remote operation.