The era of  cordless telephone system  began in 1980 and they operated at a frequency of 27 MHz, but they results in problems like poor sound quality, limited range, and poor security. Therefore in 1986, the Federal Communications Commission granted frequency of 47-49 MHz, but this also had the same problems of limited range, poor sound quality and poor security. Again in 1994 the digital cordless telephone system introduced a frequency range of 900 MHz, which allowed the phones to be more secure and this decreased eavesdropping.  In 1998, again the FCC opened 2.4 GHz and this had a frequency which increased the distance which a cordless phone can operate.