The NE556 are Dual Precision timing circuits capable of producing accurate time delays or oscillation Timing From Microseconds to Hours Astable or Monostable Operation, TTL-Compatible Output Can Sink or Source Up to 200 mA Adjustable Duty Cycle, On Products Compliant to MIL-PRF-38535, Example Applications: Fingerprint Biometrics, Iris Biometrics, RFID Reader, Precision Timers From Microseconds to Hours, Pulse-Shaping Circuits, Missing-Pulse Detector, Tone-Burst Generators, Pulse-Width Modulators, Pulse-Position Modulators, Sequential Timers, Pulse Generators, Frequency Dividers, Application Timers, Industrial Controls, Touch-Tone Encoders and a slew of other use-cases The NE556N devices are Dual precision timing circuits capable of producing accurate time delays or oscillation. In the time-delay or mono-stable mode of operation, the timed interval is controlled by a single external resistor and capacitor network. In the a-stable mode of operation, the frequency and duty cycle can be controlled independently with two external resistors and a single external capacitor.

The threshold and trigger levels normally are two-thirds and one-third, respectively, of VCC. These levels can be altered by use of the control-voltage terminal. When the trigger input falls below the trigger level, the flip-flop is set, and the output goes high. If the trigger input is above the trigger level and the threshold input is above the threshold level, the flip-flop is reset and the output is low. The reset (RESET) input can override all other inputs and can be used to initiate a new timing cycle. When RESET goes low, the flip-flop is reset, and the output goes low. When the output is low, a low-impedance path is provided between discharge (DISCH) and ground.

The output circuit is capable of sinking or sourcing current up to 200 mA. Operation is specified for supplies of 5 V to 15 V. With a 5-V supply, output levels are compatible with TTL inputs.