Editing Pendulum clock (section)

===Leveling and "beat"===
To keep time accurately, pendulum clocks must be level. If they are not, the pendulum swings more to one side than the other, upsetting the symmetrical operation of the escapement. This condition can often be heard audibly in the ticking sound of the clock. The ticks or "beats" should be at precisely equally spaced intervals to give a sound of, "tick...tock...tick...tock"; if they are not, and have the sound  "tick-tock...tick-tock..." the clock is ''out of beat'' and needs to be leveled. This problem can easily cause the clock to stop working, and is one of the most common reasons for service calls. A [[spirit level]] or [[watch timing machine]] can achieve a higher accuracy than relying on the sound of the beat; precision regulators often have a built-in spirit level for the task. Older freestanding clocks often have feet with adjustable screws to level them, more recent ones have a leveling adjustment in the movement. Some modern pendulum clocks have 'auto-beat' or 'self-regulating beat adjustment' devices, and do not need this adjustment.