Use a corded home phone whenever possible, to minimize the need for a cell phone. Cordless home phones emit RF, so replace cordless phones with corded home phones. One initial step is to unplug the electrical cord of the cordless phone base station when the phone is not in use, because otherwise that base station will emit RF nonstop. Note: you can plug a corded phone handset or corded headset into your VoIP connection.
Today, the computer and phone have merged into one device that fits in the palm of your hand. A smartphone is essentially a small computer, yet has many times the computing power of traditional computers. There are no cords to connect you to a base. When turned on in your pocket or being used against your head, the cell phone touches some of the most sensitive parts of the body. Although the cell phone produces lower levels of radiation then past computers, they are now used much closer to the body and for longer periods of time, thus creating more health risks than in the past.
The energy of electromagnetic radiation is determined by its frequency; ionizing radiation is high frequency, and therefore high energy, whereas non-ionizing radiation is low frequency, and therefore low energy. The NCI fact sheet Electromagnetic Fields and Cancer lists sources of radiofrequency radiation. More information about ionizing radiation can be found on the Radiation page.