Cordless phones offer a combination of the features of standard telephones and cell phones. They are available at affordable price ranges as standard telephones while the cordless phones also allow you to talk and move freely in your living room just like cell phones. As the cordless phone technology has made significant enhancements over the earlier models, they have become one of the sophisticated devices of modern life.

Cordless phones were introduced in early nineteen eighties. In the beginning, 27 MHz frequency band was used in the cordless phones. The lower frequency range led to basic problems like short range, constant interferences and poor sound quality. Since, these phones used fewer channels; they had poor security features that allowed signals to be easily intercepted.

The FCC (Federal Communications Commission) permitted 47-49 MHz for cordless phones in 1986. This led to the introduction of the cordless phones that were less susceptible to interferences from other devices. Still, these phones suffered from overall poor sound quality.

In 1990, 900 MHZ frequency range was granted by FCC. The phones that came in this frequency range offered clearer sound quality and longer range and were capable of choosing from multiple channels. The drawback of these phones was that they were much expensive at that time.

Four years later, in 1994, 900 MHZ cordless phones came with digital technology which provided better security features. Following year, digital spread spectrum (DSS) enabled cordless phones hit the market. These cordless phones were capable of transmitting the data between the base and the receiver in different frequencies so they offered the best possible protection to the users from eavesdroppers.

FCC introduced 2.4 GHz frequency range for cordless phones in 1998. The high frequency radio transmission enabled the cordless phones to transmit the data over much longer distances. These cordless phones also came with enhanced security features when compared with the earlier models.

A cordless telephone is made up of the components of a traditional telephone along with a transmitter that sends and receives radio signals between its base and the handset.

Base unit

The base of a cordless phone has many components that do different functions. The phone line Interface transmits the signals via the phone line. The Radio component in the base unit carries out two functions: it amplifies the signals that get transmitted between phone line interface, speaker phone and the user controls in the base. The power unit provides power for the circuit board and the battery of the handset.

The phone line interface transmits the ringer sound to the bell or to the radio component so that it gets transmitted to the handset so you know that you get an incoming call. While you are talking, the electric signals are produced and get transmitted to your caller so he/she can listen to your voice.

The main function of the radio component is to get electric signals from user controls like buttons or buttons and the phone interface and to convert the signals into radio waves of specific frequency and send them through antennae. Quartz crystals in the radio component set frequency range for both incoming and outgoing signals so that you can speak and listen simultaneously. This is called duplex frequency. There is also audio amplifier that increases the signal strength for better clarity and for long range transmission.

Handset

The handset in a cordless phone has components like microphone, speaker, keypad and a Radio transmitter . The microphone receives the sound and converts it into electrical signals. The Keypad allows you to dial the number you want to call. The speaker converts the electrical signals into the sound that you listen. The ringer, as in the base unit, allows you to know that you get a call. The radio unit amplifies and transmits the electrical signals between speaker and the microphone. There is rechargeable battery unit in the handset to provide electrical power to the handset. In addition, there are LED indicators to show the status of charging/power.

The power unit is usually made up of a DC power transformer to provide low voltage supply to the circuit board. The power cube system also helps to recharge the battery of the handset.

Battery

The rechargeable battery in the handset is usually made up of nickel-cadmium, lithium or nickel-metal hydride. If the battery is low, the LED indicator produces flashes or some handsets produce beep sounds to indicate low battery. The battery can be recharged, when you place the handset on the base unit of the cordless phone.

A few cordless phones have base unit with optional components like audio amplifiers for speakers, keypads, caller ID with liquid crystal displays, LED( light-emitting diodes) to indicate power or charging and answering machine with call-back features etc.