There are two basic methods of sync

There are two basic methods of synchronization: synchronous transmission and asynchronous transmission. In synchronous transmission, a clock signal is used as a common source of reference by both the transmitter and the receiver. By tying the data signal to the clock signal, either device can look at the clock signal to know where data bits may begin or end. The clock signal may be provided on a separate line, or be embedded in the data signal itself (see Figure 2.15). Because having a separate clock line increases the costs, it is only used for covering very short distances (e.g., for connecting personal computers).