How Telephones Become Wireless ?
Touch-Tone PhonesIn 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 PhoneIn 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.