How Do Cordless Telephones Work?

Cordless Telephones Use Microphones

The primary purpose of a cordless telephone---or, really, any telephone---is to facilitate voice conversations. In order to make this happen, a cordless telephone must be able to convert voices and other sounds into signals that can be transmitted across standard telephone lines. When you speak into the cordless telephone handset, the vibrations in the air generated by the sound cause a membrane on a small microphone in the handset to vibrate. The microphone converts these vibrations into electrical impulses. Before the electrical impulses can be sent out over the telephone lines, however, they must first be transferred to a cordless telephone base station.

Cordless Telephones Use Radio Waves

When you speak into a cordless telephone handset and your voice is converted into electricity, it must be transmitted from the handset to a base station in order to interface with the telephone network. The cordless handset sends the electrical signals generated by the microphone to the base station using standard radio waves, much like the ones used by an FM radio. The base station receives these waves using a small radio transceiver and converts them back into electrical signals suitable for transmission across the telephone network; the network is physically connected to the base station by two wires (known to telecommunications professionals as a "cable pair") contained in the telephone wire, house wiring and telephone network wiring.

Cordless Handsets and Bases Are Always Communicating

When you speak into the handset and your voice is sent across the telephone network as described above, the other party usually responds; this response requires the steps described in Sections One and Two above to be performed in reverse to receive the response, convert it into radio waves, transmit the waves from the base station to the handset, and play the sound in a small speaker embedded in the handset earpiece.

In addition to this constant communication when the phone is in use, the cordless telephone handset and base station also periodically check in with each other when no call is in progress. By initiating an electronic conversation on a predefined interval, the handset can communicate important information to the base station such as battery status, readiness for operation, proximity to the base station, and other vital data. The type of information transmitted during these sessions varies according to the specifications of the cordless telephone manufacturer, as does the frequency of the periodic updates.