Cordless handset is a phrase used to differentiate the newer types of telephone handset that send their signals wirelessly from those which are connected to the telephone base by a cord. Modern cordless handsets send and receive electronic signals via radio waves with a base unit, which is tied into the larger hardwired telephone network.
There were a few things that needed to be in place before telephone users could switch en masse to the cordless handset. First, there needed to be some kind of small onboard power source: a battery. In older, corded-style handsets, the electrical power needed to operate the phone was delivered by a wire that connected the handset to the base and the base to the larger network, or exchange. To be the most consumer-friendly, the battery for a cordless handset had to be small enough to fit into a unit of comfortable size, and the cordless handset battery had to be rechargeable. For the kind of use most phones get, running through dozens of batteries a week would have been prohibitively expensive.
Just as the batteries needed to be miniaturized, so too did the apparatus that would transmit radio signals between the telephone base--still plugged in by wire to the exchange--and cordless handset. Once it was small enough and light enough, the signal had to be privatized. A system of coding was developed that ideally acted as a lock and key between a telephone base and its cordless handset.
fNow, with a small, private radio transmitter, in reality not so much different from some encrypted walkie-talkies, all that was required was legal permission to operate cordless handsets on a dedicated slice of the radio spectrum. A coalition of telecommunications companies worked out and agreement with the government. Subsequently the world's telephone users became liberated from the tyranny of the telephone cord and its tendencies to become arbitrarily knotted and never quite reach as long as users wanted it to.
Before long, cordless handsets became the norm, with traditional corded models becoming increasingly rare. Experts predict that it will not be long before even the cordless handset becomes endangered, as fewer phone service customers elect to have landlines in their homes at all, relying on the more popular and portable cell phone instead.