Multi-frequency tone generator chip

A tone-generator system comprising a VLSI chip and ROM is presented. The prototype of the multi-frequency tone generator chip was built and performance-tested at Stanford, and is intended for use in digital telephone switches using time-division-multiplexing pulse-code modulation techniques. This tone-generator system, using digital techniques, eliminates the need for oscillators and encoders and presents a robust system on a single chip that needs no extensive adjustment in terms of the tone generator. Thus much effort, hardware and cost is saved, and a reliable and easily understood method for generating telephony signals and functions, which can be generalized to reproduce any signal where samples would be stored in the accompanying ROM, is achieved. The authors present the theory, design algorithms and structure of the chip together with the necessary directions for its large-scale production