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A method is proposed for launching and extracting the timing wave in a PAM digital transmission system, which combines the simplicity of linear self-timing, the economy in bandwidth of nonlinear self-timing, and the high performance of the added timing wave approach. The method requires that the digital signal is cyclostationary with a period which is an even multiple of the symbol period ; the simplest solution for deriving such a signal from a stationary message is to apply it to a periodically time-varying system, as a memoryless block coder. With reference to such a scheme we derive the spectrum of the timing jitter. Very simple conditions are found on block encoding in order that the encoded message exhibits the desired characteristics. Finally, ternary codes are discussed and the performance of a specific code is evaluated and compared to that of conventional extraction schemes.