Cordless Telephone

Cordless Telephone Points : Cordless Telephone set, Definition, working Radio communication systems bridge distances in the order of at least few kilometres. The cordless telephone is an extended radio communication of the telephone at home. It covers distances of a few metres or in some cases a few kilometres, depending on its output power of transmitter and height of its antenna. The cordless telephone operates in the VHF and UHF bands. The older cordless telephones used analogue transmission and s simple design. The drawback of this system is that neighbours with a cordless telephone can listen to your conversations and also they can establish calls through your base station at your expense.

This problem has been solved with digital transmission and a sophisticated system for the automatic assignment of frequencies to new calls, which offers more privacy by encryption (Encoding data to make it incomprehensible to those without a decoder) of the coded voice signal.

The cordless telephone system consists of a base unit and a portable unit. The base unit is connected to the telephone line and a power line. The portable unit consists of radio transmitter, receiver, an antenna and pushbutton keys. The portable unit operates away from the base unit. The connection of the portable unit with the base unit is through radio waves.

The base unit also consists of a transmitter, receiver, exchange interface circuit, an antenna and battery system. The transmitter of the base unit is normally off. The ringing current of the in-coming call turns ON the transmitter. The base unit with the help of radio waves radiated from the antenna gives signal to the portable unit and the subscriber is informed.

When a subscriber wants to make a call, he turns ON the transmitter of the portable unit with the help of a pushbutton and then starts dialling, just like an ordinary digital telephone. The base unit receives these dialling pulses and sends it on the telephone line. For proper communication, it is necessary that the portable unit should be within the specified range. The cordless telephones are used at home, oilfields seaport etc. The cordless telephone layout is show.