cordless telephony 1 (CT1)
In 1983, the CEPT drew up the standard for first-generation cordless telephony under the designation CT1 (Cordless Telephony 1). Predecessors of this standard were manufacturer-specific solutions known as CT0. The final CT1 standard was adopted in 1984 under CEPT guideline T/R 24-03.
CT1 operates in a frequency range of 914 MHz to 915 MHz for transmission from the handset to the fixed part, the uplink, and in the range 959 MHz to 960 MHz in the reverse direction. The channel spacing is 25 kHz, so that 40 duplex channels can be transmitted at a frequency spacing of 45 MHz using Frequency Division Multiple Access( FDMA). Channel assignment is dynamic. Before the connection is established, acheck is made to determine which frequency channels are free. Then this channel pair is reserved and the connection is established.
The transmission power of the analog modulated signal is a maximum of 10 mW, which corresponds to a range of 50 meters indoors and 300 meters outdoors.
To prevent unauthorized use of the fixed part by third-party cordless phones, the standard provides for more than 1 million identification codes between the mobile and fixed part for unique identification and is constantly checked by inner-band signaling.
Since the GSM standard, which was adopted later, also uses frequencies in the 900 MHz range and can therefore cause interference, it was decided by EC decision that cordless telephony would no longer be allowed to transmit in the 900 MHz range until 2001.
CT1 became the standard in various countries around the world, and variants with reduced channel widths exist. The first variant of CT1, developed by Deutsche Telekom, is CT1+. With 80 channels, this standard has twice the number of channels and transmits in the uplink at 885 MHz to 887 MHz and in the downlink at 930 MHz to 932 MHz. Like CT1, CT1+ operates in analog mode with frequency shift keying.