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== AMPS ==== [[AMPS]] ==This technology is mentioned for historical purposes. Although radio phones or a proto cell phone technology can be traced back to the 1950s, Advanced Mobile Phone System (AMPS) is considered the first true cell phone network commercially available to the United States, starting in 1978. {{:AMPS}}AMPS communication was unencrypted, so people to listen in on cell phone conversations with an ordinary police scanner. Phones were often cloned, causing issues of fraud and network abuse. AMPS was also a bandwidth hog, using a Frequency-division multiple access (FDMA) scheme that required significant amounts of wireless spectrum.== [[GSM]] ==AMPS started to get phased out beginning in the 1990s when PCS digital was introduced. [[GSM]] stands for Global System for Mobile Communications; it's the world's most prolific mobile standard. This is what you will find if you are, say for example, traveling in Europe. Verizon Wireless operated an AMPS network, and on February 18, 2008, Verizon discontinued all AMPS service. The last of the AT&T AMPS network was shut down February 18, 2008. == GSM == GSM stands for Global System for Mobile Communications; it's the world's most prolific mobile standard. This is what you will find if you are, say for example, traveling in Europe. == CDMA ==== [[CDMA]] ==CDMA stands for Code Division Multiple Access, including both CDMAOne or CDMA 2000. This is the most common standard in the United States of America throughout the 1990's and until present (2012).[[CDMA]] stands for Code Division Multiple Access, including both CDMAOne or CDMA 2000. This is the most common standard in the United States of America throughout the 1990's and until present (2012).This is an outdated technology. The major TDMA carriers switched over to GSM. AT&T (including the former AT&T Wireless) and US Cellular were formerly on the TDMA standard. US Cellular actually went to CDMA. This is an outdated technology. The major TDMA carriers switched over to GSM. AT&T (including the former AT&T Wireless) and US Cellular were formerly on the TDMA standard. US Cellular actually went to CDMA. === iDEN === Sprint Nextel provided iDEN (Integrated Digital Enhanced Network) service across the United States, but its iDEN network was decommissioned on June 30, 2013. iDEN places more users in a given spectral space, compared to analog cellular and two-way radio systems, by using speech compression and time division multiple access (TDMA).Verizon's phones and network are CDMA, which doesn't use sim cards. {{:CDMA vs GSM}} CDMA phones do not use sim cards, while GSM phones do. CDMA and GSM are different technologies that are incompatible with each other. The term "unlocking" referring to an unlocked phone is used when discussing GSM and iDEN phones. There are other CDMA providers besides Verizon, which include Sprint and US Cellular. Verizon will only activate another Verizon phone. A non-Verizon CDMA phone's ESN number will not be in Verizon's database of phones, and therefore, Verizon will not activate it. Verizon will also blacklist a [[Bad Verizon ESN Number]] on a formerly valid Verizon phone for certain reasons, which brings attention to one important caveat when buying a used Verizon phone.[[Category:Telephone]]