InformationWeek SMB TechEncyclopedia

(1) (Radio Frequency) Definition #2 below explains radio frequencies; however, the term may be used to contrast wireless transmission systems that do not require line of sight with those that do. For example, an RF remote control does not require line of sight to the device it is controlling (see RF remote control). See line of sight and RFID.

(2) (Radio Frequency) The range of electromagnetic frequencies above the audio range and below infrared light (from 10 kHz to 300 GHz). Except for infrared (IR) transmission, all wireless transmission uses RF, including AM and FM radio, TV, satellites, portable phones, cellphones and wireless networks. RF signals can be focused in one direction (directional), or they can transmit in all directions (omnidirectional).

Frequency and Power
The range of frequencies and power output determine how well RF signals can penetrate walls and other objects. Signals up to 2 GHz can generally go through dense objects, but from 2 GHz to 5 GHz, they have some difficulty. From 5 GHz to 50 GHz, signals require line of sight, but can traverse long distances. Signals above 50 GHz require line of sight, but only for short distances. See RF modulation, RF shielding, RF remote control and ISM band.