Telephone Communications

What radio frequencies does a cordless phone use?
Answered by Science Channel
  • Science Channel

    Science Channel

  1. When cordless phones were introduced in the 1980s, multitaskers rejoiced -- such as moms trying not to strangle the toddlers balanced on their hips while they heated bottles and talked on the phone. Little did they know that the range and clarity of those phones would outshine their bulky first generation counterparts in a few short decades. They also could not foresee that their children might one day shun cordless phones altogether for their more powerful cousin: the cell phone.

    Many homes and businesses that still have land lines today own cordless phones, however. The first cordless phones had frequencies of about 1.7 megahertz (MHz). They used telescoping antennas to help pick up the wireless signal from their bases. Today's cordless phones can operate on several different frequencies, which are set by the Federal Communications Commission (FCC). The agency maintains and assigns bands for all sorts of communications frequencies, including amateur radio service, aviation, television transmission and mobile satellite service [source: FCC Spectrum Bands]. The following frequencies are set for cordless phones:

    • The next generation (after 1.7 MHz) of early cordless phones used the 43 MHz to 50 MHz band, which might be found today in less expensive models. Phones using these frequencies have short ranges, poor sound quality and signals that can be easily intercepted.
    • In 1994, the FCC released the 900 MHz band, which was the most common frequency for phones for many years. These phones had greater sound quality and range, but their signals also could be easily intercepted.
    • The 2.4 GHz frequency band was opened for phones by the FCC in 1998. By 2003, the 5.8 GHz band also was added because the 2.4 GHz frequency was so crowded, not just with phones but with devices such as microwave ovens [source: Pedro]. Phones using 2.4 GHz and 5.8 GHz frequencies have a wide operating range, and their calls are much more secure because most commercial radio scanners can't pick up the signals.

    For security, a minimum of 2.4 GHz probably is the best bet to ensure phone calls aren't picked up by scanners, or baby monitors, which can run on the same frequencies as some cordless phones.

     

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