the search state. Figure 1.17 shows an example where the scanning starts from point a. The imitation of the FAW is represented by I in the figure. At the beginning, when the scanning process starts (point a), there is no previous alignment, and therefore the system starts in a search state. During this state the bit sequence is scanned to find the FAW pattern. In the example shown in the figure, the first FAW happens to be imitated by information bits (point b). Therefore, the system assumes that a FAW is found and by mistake enters a waiting state. Chapter 1 Voice Transmission Frame 1 Frame 2 Frame 3 Frame 4 One Frame Fig. 1.17 Example of the frame alignment procedure. However, because there is no FAW at one frame distance from point b (point c), the system returns back to the search state at point C. At point d the system again enters the waiting state. However, the state does not change until the third correct alignment word is recog- nized at point e, where the system starts operating in full-synchronized mode. Notice that the imitation between points d and e has no effect. In fact, when a partial synchronization is established, the system stops searching for the FAW pattern and only checks the frame alignment pattern every frame interval. The serial alignment algorithm can be implemented in a very simple fashion; however, performance (in terms of average search time) can be improved by using parallel searching. Parallel searching can minimize the impact of frame alignment imitation by selecting all possible FAWs (the real or imitated) and rejecting the ones that are not repeated after a frame interval, though this advantage might not be very significant, especially when imitations of FAW occur rarely. Another interesting property is the stability of the system against the transmission errors. In fact, when the system enters a full-synchronization state, the occasional bit cor- ruptions of FAWs cannot return the system to the search state; this later event occurs only if a FAWs is corrupted during some number