Digital signal generation circuit for telephone - includes second high frequency square wave cutting lower frequency wave to produce modulated output tone

摘要

The generator comprises a signal cutting circuit (X2) in which an input signal (Q1) having a first fundamental frequency (500 - 16,000Hz) is cut by a second signal (Q2) having a higher fundamental frequency (32,000Hz). This produces an output comprising the cutting signal modulated by the first input signal. - The input signal is a square wave, and the cutting signal is a rectangular wave having a frequency which is an even multiple of the first frequency. The frequency sprectrum of the output signal is only affected by that of the input signal.