The cordless phone is an FM transmitter/receiver. The frequency range lies between 26.6 and 49.8 MHz A cordless phone essentially converts the audio signals from the telephone line into the FM waves and it is detected by the mobile handset, and vice versa. For security reasons the range is limited to about 100 metres and their power is about 500 milliwatts. Each cordless phone is assigned a particular channel (or frequency range) to avoid interference with nearby instruments.
Cordless phone is based on wireless transmission and frequency modulation. The main components of a cordless phone are the base unit and the portable unit. While the base unit is kept at a fixed point, connected to power supply and the working telephone line, the portable unit can be carried to a certain distance, depending on the frequency range limitation. Normally in India, the permissible distance is about 100 metres.
The base unit and the portable unit essentially consist of radio wave transmission and reception devices which enable a two way wireless communication between these units.
The radio waves are broadcast in the air through the antenna fitted to the units. Just like the signals emanating from the telephone are converted to radio frequency in the transmission side, the reverse happens in the receiver side, (i.e.) the radio frequency signals are converted into original signals, bell or speech.
Since the handset does not have and connecting cord or wire, the name cordless phone.