## Symbol timing circuits (cont)

#### An alternative symbol timing recovery circuit involves 'squaring' the received filtered data stream, which yields a signal with a strong discrete frequency component at the symbol timing frequency. Extracting this signal with a narrow tuned filter or a phase locked loop gives the required symbol clock. This system works well for a = 1.0, but will not produce a discrete spectral line for small values of a. #### Yet a third method of symbol timing recovery is the early-late gate method. This technique is described in connection with amplitude shift keying in Chapter 5. |