This document discusses multiplexing and spreading techniques. It describes multiplexing as a set of techniques that allows simultaneous transmission of multiple signals over a single data link to maximize bandwidth utilization. Frequency-division multiplexing (FDM), wavelength-division multiplexing (WDM), and time-division multiplexing (TDM) are discussed as categories of multiplexing. Spread spectrum is described as combining signals from different sources to prevent eavesdropping and jamming through redundancy. Frequency hopping spread spectrum (FHSS) and direct sequence spread spectrum synchronous (DSSS) are introduced as spread spectrum techniques. Examples of applying these concepts are provided through diagrams and calculations.