Digital tone generator

A digital tone generator adapted to be connected to a digital telecommunication system for simultaneously generating during a tone generator operation cycle digital encoded instantaneous amplitude values of a variety of continuous and of cyclically repeated discontinuous tone signals each composed of at least one frequency component and assigned to a separate tone channel of a tone highway representing a time-division multiplexed serial data transmission line, said digital tone generator comprising:

• (a) sequencing control means for generating a consecutively incremented and cyclically repeated reference address signal directing the course of said operating cycle;
• (b) amplitude control means for generating amplitude control signals determining varying mean amplitude values of discontinuous digital tone signals such that stepwise adjusting of a mean amplitude value takes place coincidentally with the instantaneous amplitude going through zero value and in accordance with a predetermined attenuation curve at the commencement of the rising and trailing ends of a pulse of each discontinuous digital tone signal, said amplitude control means including at least one input connected to receive said reference address signal, storage means for storing steady and variable amplitude control information, processing means for producing said amplitude control signals, and at least one input;
• (c) amplitude value generating means including a phase value generator connected to receive said reference signal for producing an instantaneous, frequency dependent phase value signal constituting a current sine address signal;
• and including a single sine wave generator incorporating a sine wave memory in form of a random access memory provided with a multiplicity of memory locations each permanently storing one of consecutive sine amplitude values having a finite difference from each other such that these values represent a continuous part of a single sine wave form, said memory for storing sine wave amplitude values having address inputs connected to receive the sine address signal and read outputs wherein said amplitude value generating means are further connected to receive said amplitude control signals for generating a digital encoded signal representing one of said instantaneous amplitude values;
• and
• (d) output means connected to receive said digital encoded signals for transmitting said digital encoded signal onto said tone highway in synchronization with the cyclical occurrence of the assigned tone channel.