An early standard for analog cordless telephony developed by the European Conference of Postal and Telecommunications Administrations (CEPT) in Europe, where it was known as CEPT-1. CT1 operates in the 915 MHz and 960 MHz bands over 40 paired channels 25 kHz wide and employs frequency modulation (FM). Frequency division multiple access (FDMA) and frequency division duplex (FDD) are used to derive two separate channels, one downstream and one upstream, each of which is 12.5 kHz wide. CT1 is limited in range to approximately 150 meters. A variation on this standard is CT0, which was primarily used in the United Kingdom. See also analog, CEPT, channel, cordless telephone, CT0, downstream, FDD, FDMA, FM, and upstream.
A variation on the early CT1 standard for analog cordless telephony, CT1+ was developed jointly by Belgium, Germany, and Switzerland. CT1+ was intended as the basis for a public wireless service, along the lines of Telepoint. CT1+ operated in the 887 MHz and 932 MHz bands over 80 channels 25 kHz wide, with one channel per carrier. CT1+ employed frequency division multiple access (FDMA) and frequency division duplex (FDD) to derive two separate channels per conversation, one for downstream and one for upstream transmission, each of which is 12.5 kHz wide.Although CT1+ was not successful, it originated the concept of a common air interface (CAI), which enables multiple manufacturers to develop products in support of a public cordless telephony service offering. See also air interface, analog, carrier, channel, cordless telephone, CT1, downstream, FDD, FDMA, Telepoint, upstream, and wireless.