Candle clocks were also used by King Alfred the Great of England and in medieval churches. Candle clocks were not reliable timekeepers due to variations in the burning rates of candles. An alarm clock was set up by inserting a nail in the candle, then putting the candle in a metal dish.
An electric clock is a clock that is powered by electricity, as opposed to a mechanical clock which is powered by a hanging weight or a mainspring. The term is often applied to the electrically powered mechanical clocks that were used before quartz clocks were introduced in the 1980s.
The incense clock (simplified Chinese: 香钟; traditional Chinese: 香鐘; pinyin: xiāngzhōng; Wade–Giles: hsiang-chung; literally: "fragrance clock") is a Chinese timekeeping device that appeared during the Song Dynasty (960-1279) and spread to neighboring East Asian countries such as Japan and Korea.
A pendulum clock is a clock that uses a pendulum, a swinging weight, as its timekeeping element. The advantage of a pendulum for timekeeping is that it is a harmonic oscillator; it swings back and forth in a precise time interval dependent on its length, and resists swinging at other rates.
Water clock. A water clock or clepsydra (Greek κλεψύδρα from κλέπτειν kleptein, 'to steal'; ὕδωρ hydor, 'water') is any timepiece in which time is measured by the regulated flow of liquid into (inflow type) or out from (outflow type) a vessel where the amount is then measured.