NE556N DIP IC

Pin Number	Pin Name	Description
1,13	Discharge	Open collector output which discharges a capacitor between intervals (in phase with output). 7 I It toggles the output from high to low when voltage reaches 2/3 of the supply voltage
2,12	Threshold	Compares the voltage applied to the terminal with a reference voltage of 2/3 Vcc. The 6 I amplitude of voltage applied to this terminal is responsible for the set state of the flip-flop
3,11	Control Voltage	Controls the threshold and trigger levels. It determines the pulse width of the output 5 Voltage I waveform. An external voltage applied to this pin can also be used to modulate the output waveform
4,10	Reset	Negative pulse applied to this pin to disable or reset the timer. When not used for reset 4 I purposes, it should be connected to VCC to avoid false triggering
5,9	Out	This pin is normally connected to load as it is the only pin with output driven waveform
6,8	Trigger	Responsible for transition of the flip-flop from set to reset. The output of the timer depends 2 I on the amplitude of the external trigger pulse applied to this pin
7	Ground	Ground Reference Voltage 0V
14	Vcc	Supply Voltage (Typical = 5V, Maximum = 18V)