CT0 (Cordless Telephony 0) is the first system for cordless telephony operated in the USA and Asia in the 1970s. It was not a standard, but national solutions that were very much proprietary on the part of the manufacturers.
The various development approaches were adapted to each other over the course of time. In addition to the U.S. solution, there are national CT0 procedures with some variations in France, the Netherlands, Spain and the United Kingdom. The differences mainly concern the number of channels and the transmission frequencies. Since the transmission in the CT0 network was easy to eavesdrop on, and there was also the possibility of accessing long-distance networks via foreign base stations, this procedure was not approved for wireless telephony in the European countries not mentioned.
The CT0 system was not a cellular network; it operated in the frequency range from 1.6 MHz to 47 MHz with analog transmission and FDMA procedures. The range between the fixed part and the handset was up to one kilometer. Only one user could be connected per system.