Although data are processed in parallel in many digital systems to achieve faster processing speeds, when it comes to transmitting these data relatively large distances, this is done serially. The parallel arrangement in this case is highly undesirable as it would require a large number of transmission lines. Multiplexers can possibly be used for parallel-to-serial conversion. one such arrangement where an 8-to-1 multiplexer is used to convert eight-bit parallel binary data to serial form. A three-bit counter controls the selection inputs. As the counter goes through 000 to 111, the multiplexer output goes through I0 to I7. The conversion process takes a total of eight clock cycles. the three-bit counter has been constructed with the help of three toggle flip-flops. A variety of counter circuits of various types and complexities are, however, available in IC form.