cuitry, were significantly more expensive than their nontrunked predecessors. Most of this work was conducted during the turbulent 1960s and led to Bell Labs' introduction of Improved Mobile Telephone Service (IMTS). IMTS used two 30 kHz, narrowband FM channels for each conversation, and provided full-duplex talk paths, direct dialing, and automatic trunk- ing. Introduced commercially in 1965, IMTS is considered to be the pre- decessor of modern cellular telephony. The Spectrum Battles Heat Up Starting in the mid-1940s, mobile telephony went head-to-head against the television industry in a pitched battle for spectrum. In 1947, the Bell System proposed to the FCC a plan for a large-scale mobile telephone system, asking them to allocate 150 two-way, 100 kHz channels. The pro- posal was not accepted. In 1949, while the FCC wrestled with the assignment of spectrum in the 470 to 890 MHz range that would become UHF television, the tele- phone industry argued that they should be granted a piece of the elec- tromagnetic pie. Their issue was that the 6 MHz of bandwidth required for a single TV channel was more than had ever been allocated for mobile Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Access Technologies Chapter 6 telephony. Unfortunately, television had penetrated the American house- hold-Captain Kangaroo, Roy Rogers, and Winky-Dink captivated view- ers, and consumers were hungry for additional programming. Wireless telephony wasn't even on their radar screens; it would have to wait. In the 20 years that followed, mobile telephony continued to take a backseat to television. UHF usage grew slowly; in 1957 the Bell System petitioned the FCC to give them a piece of the earmarked spectrum in the 800 MHz range that was virtually unused. But television was still the darling of the nation, and the FCC was ferociously dedicated to expanding the