Two channel telephone system using pulse frequency modulation

Abstract

This work is concerned with the analysis, design and construction of a two channel telephony transmission system using 'Pulse Frequency Modulation' within 'Time Division Multiplexing'. The current widespread use of digital signalling is the result of many factors: (1) The relative simplicity of digital circuit design and the ease with which one can apply integrated circuit techniques to digital circuitry. (2) The ever increasing use and availability of digital processing techniques. (3) The widespread use of computers in handling all kinds of data. (4) The ability of digital signals to be coded to minimize the effects of noise and interference. Although some communication signals are inherently digital in nature -- eg. teletype data, computer outputs, pulsed radar and sonar signals -- many other signals are analogue, or smooth, functions of time. If these signals are to be transmitted digitally, they first have to be sampled and each sample made to vary some parameter of an unmodulated pulse train.