Copyright Goodheart-Willcox Co., Inc. 48 Networking Fundamentals Network Media Network media is a general term for the various ways to transmit data. Th ere are two general classifi cations of network media: cable-based and wireless, as shown in Figure 2-1. Cable-based network media comprises copper-core cabling, such as co- axial and twisted pair, and glass or plastic core cabling, such as fi ber-optic. Wireless network media comprises air, or the atmosphere. All network communication originates from electronic signals. However, some media translates that into other types of signal. For example, fi ber-optic uses light waves to transmit data. Wi-Fi uses radio waves to transmit data. Coaxial and twist- ed-pair cable use pulsating electrical energy to transmit data. To understand the terminology related to network media and network commu- nication, you must fi rst learn some basics about electronic signals. In the following section, we will look at the characteristics of two general types of electronic signals: analog and digital. 2.1 NET Network media Cable-based Wireless Copper core Fiber-optic cable Atmosphere Coaxial cable Twisted- pair cable Radio waves Light waves Electrical energy Infrared Microwave Glass/plastic core General Classification Major Classification Media Type Electronic Signal Figure 2-1 Network media classifications and media types. At the bottom of the hierarchy are the types of electronic signals that each media type carries. Goodheart-Willcox Publisher Analog and Digital Signals An analog signal is a signal that has a continuous range of values, much like a wave. Radio signals and light are common examples. A digital signal is a signal that has discrete values of on or off . Electrical transmissions often represent this by one volt- age being a 1 and another voltage being a 0. However, analog signals must also contain digital information. You have prob- ably used Wi-Fi, which depends on radio transmissions, which are analog. However, analog signals can be used to transmit digital information. Th is is done by using some aspect of the analog signal to represent a digital value. For example, the wavelength can be used. One range of wavelength represents a 1 and another represents a 0. Amplitude modulation is another method of encoding digital data into an an- alog signal. With this method, one specifi c amplitude represents a 1, and another represents a 0. Th e same thing can be accomplished with frequency modulation, with one frequency representing a 1, and another representing a 0.