Radio frequency oscillation is between 30 KHz (kilo hertz or 1000 cycles per second) and 300 GHz (Giga hertz or 1.0 billion cycles per second). Alternating current (AC), unlike direct current (DC), possesses a special property by radiating electromagnetic waves from a conductor; this is the basis of RF technology. Different frequencies propagate through different medium for varying distances; for example, some high frequency (HF; 3 to 30 MHz) and very high frequency (VHF; 30 MHz to 300 MHz) systems may transmit signals of more than 90 feet.