Abstract: A pulse code modulation (PCM) modem system employs a relatively white training signal to optimize the adaptive filter coefficients in the receiver equalizers. During the training mode, any line coding or equivalent spectral shaping is disabled to provide a training signal sequence having a substantially even spectral content. The presence of DC within the training signal reduces the likelihood that the error function of the equalizers will settle at a local minimum. Following the training interval, the encoder enables the line coder to condition the digital input sequences, introduce DC nulls, and reduce the detrimental effects of baseline wander.