eaus. Throughout the 1960s, 1970s, and well into the 1980s, microwave radio spectrum carried the majority of US long distance traffic. Radio transmission capacity became the growth engine of the long distance telephone industry. MCI applied for and received a license to carry long dis- tance traffic between Chicago and St. Louis, eventually building a nationwide analog radio transmission network. AT&T had a combin- ation of digital and analog radio transmission capacity when entered into to its third consent decree with the justice department in 1982. Most of the digital radio capacity was in the access network in intra-state service. By the end of the century, those radio transmis- sion networks have for the most part been decommissioned and replaced with fiber transmission capacity. PRACTICAL IP AND TELECOM FOR BROADCAST ENGINEERING AND OPERATIONS Until computers came into the picture, transmission was all analog. Audio, video, speech, or other information was carried in basic or baseband form on wire, or modulated on to some type of carrier-a separate, single, much higher frequency signal, transmitted, received, demodulated, and applied to a speaker or display device. Long before computers placed demands on the communications network, voice was digitized and the resulting signals multiplexed to gain more usage on common trunk facilities. As computers increased in capability and created demand for connections to terminals and other computers, the digital signal interface to the network was the natural common sense approach; however, that was not to be for many years. Digital transmission techniques include various forms of carrier modulation in wireless, including amplitude, frequency, and phase. Modems (acronym for modulator-demodulator) are a required function and, in some cases, a separate item of equipment in satellite earth station equipment complements. The function of these devices is to impress upon, or modulate, the carrier signal with the baseband signal, or digital bitstream. Modem functions mirror, 