The 555 timer IC is an integrated circuit (chip) used in a variety of timer, pulse generation, and oscillator applications. The 555 can be used to provide time delays, as an oscillator, and as a flip-flop element. Derivatives provide up to four timing circuits in one package. The 555 is still in widespread use due to its low price, ease of use, and stability.. As of 2003, it was estimated that 1 billion units are manufactured every year. The 555 is the most popular integrated circuit ever manufactured.