Cell blocked (or cellular blocked) is a phrase applied to scanners and wideband receivers manufactured for sale in the US which denotes that they comply with the provisions of PL 102-556, which amended Section 302 of the Communications Act 47USC302 - to prohibit manufacture, importation, or certification of scanners which could receive the frequency band allocated for analog AMPS - a type of Mobile Phone Network Technology, "the frequencies allocated to the domestic cellular radio telecommunications service":
It was in April of 1994 that the FCC mandated all manufacturers had to build the radio scanners with a block against scanning any cellular frequencies. The law is now useless since all cellphones currently in use in the U.S.A. are now digital, so an analog receiver won't receive them in a useful way. There isn't a known consumer scanner ever made that can be modified to receive and decipher the current digital cellphones used today.
Cell phones today use none of which are relevant to the old regulation.
- CDMA - Verizon, Sprint, US Cellular, MetroPCS
- iDEN - Nextel, Boost, Telus
- GSM - ATT, TMobile
- WCDMA / UMTS - ATT, TMobile
- LTE / EVDO / 4G, 3G, 1x (related terms)
None of these technologies are decodable by an analog scanner, therefore the block is no longer necessary.
Because there are receivers, such as police scanners, that are not Cellular Blocked, people often wonder how the regulation is being circumvented. Those models that are floating around are either old, manufactured before the regulation, or new units that are not meant for United States distribution, such as the so called export market, or receivers coming into the country under the radar. There are units manufactured specifically for government use. Government model units will not be cellular blocked. It is unlawful for a shop to sell used older model receivers capable of receiving on the blocked frequencies even though there is absolutely nothing to monitor on those frequencies anymore; as stated previously, the cell industry no longer uses AMPS. HAM radio groups have been requesting the FCC lift the restriction as it is no longer relevant. Today the FCC mandate is nothing more than an annoyance to radio enthusiasts and manufacturers.