NE555P (NE555 series) General-purpose single bipolar timers (DIP)ST Microelectronics
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.
For more information, have a look at :
- The wikipedia page : http://en.wikipedia.org/wiki/555_timer_IC
- The datasheet : http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00000479.pdf
- The tutorial for hooking it up to an Arduino : http://www.buildcircuit.com/blinker-using-arduino-and-ne555-timer-ic/