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Alternatives to single sideband modulation are sought for the most efficient use of the voice-band channel in data transmission. Under a certain criterion on optimum data pulses, the direct use of the passband is as efficient as the conventional use of single sideband, which converts the available passband into an apparent lowpass channel. With the simultaneous practical constraints of distortionless transmission, strict passband limitation, and a spectrum free of discontinuities, the principles of pulse-shaping used at lowpass are also applicable for a passband. A class of bandpass pulses is derived which achieves, in addition, a firstorder immunity to timing jitter in the receiver clock, an important property for multilevel PAM systems. Extension to passband is discussed for duobinary transmission.