How Telephones Become Wireless ?

 How Telephones Become Wireless ?

Touch-Tone Phones

In 1941, the first touch-tone system that used tones in the voice frequency range rather than pulses generated by rotary dials was installed in Baltimore, MD. 

Cordless Phone

In the 1970s, the very first cordless phones were introduced. In 1986, the Federal Communications Commission or FCC granted the frequency range of 47-49 MHz for cordless phones. Granting a greater frequency range allowed cordless phones to have less interference and need less power to run. In 1990, the FCC granted the frequency range of 900 MHz for cordless phones.
In 1994, digital cordless phones and in 1995, digital spread spectrum (DSS) were both respectively introduced. Both developments were intended to increase the security of cordless phones and decrease unwanted eavesdropping by enabling the phone conversation to be digitally spreadout. In 1998, the FCC granted the frequency range of 2.4 GHz for cordless phones and as of 2003 the upward range is now 5.8 gigahertz.

• How Cordless Telephones Work
  How cordless phones work and a brief history of cordless phones.

Cell Phones

In 1947, research into cell phones technology began with an examination of the limited mobile (car) phones of the times. Scientists realized that by using small cells (range of service area) with frequency reuse they might be able to increase the traffic capacity of mobile phones substantially.