A sequential circuit for the control of an all-digital multiline data set is presented. Such a circuit, operating in conjunction with a digital modulator and demodulator, is necessary to provide the scanning, timing, display, and interface control features associated with the exchange of information between

voice-band communication channels and their associated business machine ports. This paper discusses the design of the control circuit as a sequential machine, traces its development starting with a word statement of the problem in the form of flow diagrams, and ends with the logic equations upon which the hardware design is based.