Audible tone generation in PCM telephone exchange - storing operative frequencies as digital bit code in memory

摘要

The proposed tone signal system uses the power and memory of a microprocessor to reproduce the tones on demand without having to switch in an analog signal generator. The analog signal representing the typically multifrequency tone is generated in an oscillator (SWE). A converter (C) controlled by a clock or pulse generator (TG) changes this signal into a bit pattern by a sampling method. The same clock also enters this now digital signal into a memory (Sp) to a set time pattern. The memory forms part of a microprocessor. The time divisions are spaced at typically 125 microseconds. By reading out the stored information the desired tone can be synthesised. Inside the time interval several different tones can be stored, and by selecting the read out the processor can be ordered to reproduce the desired tone. The system may be realised using a single chip processor.