Digital Timers 555 Timer Features of 555 Timer IC 555 Timer Construction & Block Diagram 555 Timer Pinout Configuration Schematic & Working Principle of 555 Timer Internal Function Diagram of 555 Timer 555 Timer Internal Schematic diagram Types of 555 Timers & Operating Modes Monostable Mode: Astable Mode: Bi-Stable Mode: Timer Calculator Applications of 555 Timer