AMPS, or Advanced Mobile Phone System, is an early analog mobile phone standard that was widely used in the United States during the 1980s and 1990s. It allowed for voice communication over radio frequencies and was one of the first systems to enable mobile telephony. AMPS operated on a frequency range of 800-900 MHz and used a technique called frequency division multiple access (FDMA) to allow multiple users to share the same frequency band. As technology advanced, AMPS was eventually replaced by digital systems like GSM and CDMA, which offered improved call quality, security, and capacity. The transition to digital networks marked a significant evolution in mobile communication, paving the way for modern smartphones and data services. AMPS was officially phased out in the U.S. by 2008, but its legacy remains in the development of mobile technology.