The 555 timer IC is one of the most common ever made. It is a simple timer and oscillator that turns up in all kinds of circuits. Commonly used to generate tones, increment counters and blink lights. 4.5-16V supply with TTL compatible output.
This is a common 555 timer/oscillator from TI. A classic for all of those first year circuits projects where you need to blink an LED, generate tone, and thousands of other great beginning projects. Google around for a huge list of resources and example projects.
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