Timekeepers, not classified elsewhere in the Chapter, essentially constructed for indicating the time of day; they must, therefore, have movements other than watch movements. Clocks and alarm clocks with watch movements. The clocks classified here may be weight, spring, electrically or electronically operated; they are generally regulated by a pendulum, a balance-wheel and hairspring, a tuning fork or a piezo-electric quartz crystal. They are often equipped with a striking mechanism (hours, alf-hours, or quarters) acting on a bell or gong, or a multi-gong chiming mechanism.