This document provides an overview of analog communication systems and focuses on angle modulation techniques, specifically frequency modulation (FM) and phase modulation (PM). It defines these modulation techniques and discusses key concepts such as modulation index, frequency deviation, bandwidth, and Carson's rule for calculating FM bandwidth. Narrowband FM is used for applications requiring a small bandwidth like short-range communications, while wideband FM is used for entertainment broadcasting where higher quality transmission is needed and bandwidth is not a constraint. FM can be represented in either the time domain by showing the continuous variation of the carrier signal over time, or in the frequency domain using a spectrum that plots the amplitudes of the carrier and sideband frequencies.