1. A system for recording digital information on a record medium using a writing source, comprising: means for receiving an input signal to be recorded; means for sampling and formatting the input signal to produce successive samples indicative of the input signal; a mark pulse width modulator, receiving a first series of samples, and producing an output pulse of a logical "1" level, having a discretely variable time duration corresponding to each successive sample of the first series; a space pulse width modulator, receiving a second series of samples, and producing an output pulse of a logical "0" level, having a discretely variable time duration corresponding to each successive sample of the second series; controlling means for alternately enabling said mark pulse width modulator and said space pulse width modulator and for combining said logical "1" level and logical "0" level pulses from said mark pulse width modulator and said space pulse width modulator into a continuous stream of pulses of opposite polarities, so that each two immediately adjacent output signals from said controlling means include one pulse of said logical "0" level immediately adjacent to another pulse of said logical "1" level; and means for using said continuous stream of pulses to modulate an output of the writing source to write on the record medium.