Components: NOT gates, digital sources, D flip-flops Theory: There are several applications in digital systems where non-binary counters required. These counters output a decoder-like sequence. These are used to identify specific time instances. A non-binary counters called ring counter can be designed using shift registers. A circular shift register initialized such that only one of its flip-flops is at 1 state is called a ring counter. Upon application of each clock pulse, the 1 is shifted around the register. An n-stage ring counter has n states.