Cordless telephones have evolved over time into sophisticated consumer electronics devices. With each iteration of technology, the radio frequency a cordless telephone uses has increased, to help avoid interference problems and eavesdropping via neighbors' phones and radio scanner users.
Cordless Phone Frequency Bands
- 1.7 MHz - The earliest analog models used this frequency band, just above the AM broadcast band. They are no longer in production, and were very susceptible to interference from fluorescent lights and nearby automobile ignition systems.
- 46 MHz - 47 MHz - This band contains a huge installed base of analog models. Low-power walk-talkies and baby monitors share this same frequency band of 25 channels (frequencies). Some models use audio inversion for scrambling. The unscrambled models are very easily heard by practically any radio scanner. Or a neighbor with a similar phone can listen in on your frequency. This band can be quite crowded, depending on the density of users in a given area.
- 902 MHz - 928 MHz - The newer models, readily identified by their shorter, non-telescoping antennas, use the "900 MHz" band. Only the models with digital spread spectrum (DSS) cannot be readily heard by a radio scanner. The rest are all analog models that are easy to pick up. This band is much less crowded than the 46-MHz to 47-MHz band. This generation of cordless telephones enjoys 80 channels. Each manufacturer uses some but not all of the available channels.
- 2.7 GHz - The very latest models operate in the 2.7-GHz band. Few radio scanners cover this band, and analog and digital spread spectrum models are available to ensure privacy.
If you are buying a new cordless phone, buy one that operates in the 900-MHz or 2.7-GHz band using digital spread spectrum technology for privacy and longer range.