The CD4017 counter is an integrated circuit that switches on ten outputs one at a time, due to a clock signal on the input pin 14. The input pin 13 enables the clock signal, while the input pin 15 is supposed to reset the output condition.
An input pin features the high level when it is supplied with a positive signal. As you can see in the image an input pin can be connected to a button-resistor series, or else to an output. This one features the high level when it puts out a positive signal. Basically an output works like an SPDT switch does, but actually there aren’t mechanical switches inside an integrated circuit.
Once the CD4017 is supplied the first output switches on. If the clock pin takes for an instant the high level and the input pins 13 and 15 are both low, the first output switches off, while the second one turns on. When the last output turns off the cycle repeats. If the reset pin takes for an instant the high level the CD4017 backs to the start condition. If the input pin 13 features the high level, the counter ignores the clock signal. If not used the input pins 13 and 15 must be connected to the negative power supply.
The CD4017 usually works with a power supply between 5 and 18 Volts. Its outputs can support a small current (up to 20mA).
Since the CD4017 counter is a logic integrated circuit, it is very sensitive to static electricity.