Credit: ccarlstead CC-BY 2.0. Playing cards developed their four-suit design in the 1480s in France. By the late 1800s, factories mass-produced standard English playing cards that featured diamonds, hearts, clubs and spades, a design that prevails as of September 2014. Older cards were based on Latin suits of cups, swords, coins and rods.
Definition - What does Spread Spectrum mean? Spread spectrum is a technique used for transmitting radio or telecommunications signals. The term refers to the practice of spreading the transmitted signal to occupy the frequency spectrum available for transmission.
The best-known use of radio waves is for communication; television, cellphones and radios all receive radio waves and convert them to mechanical vibrations in the speaker to create sound waves that can be heard. Electromagnetic radiation is transmitted in waves or particles at different wavelengths and frequencies. This broad range of wavelengths is known as the electromagnetic (EM) spectrum. The spectrum is generally divided into seven regions in order of decreasing wavelength and increasing energy and frequency. The common designations are radio waves, microwaves, infrared (IR), visible light, ultraviolet (UV), X-rays and gamma-rays. Radio waves have the longest wavelengths in the EM spectrum, according to NASA, ranging from about 1 millimeter (0.04 inches) to more than 100 kilometers (62 miles). They also have the lowest frequencies, from about 3,000 cycles per second or 3 kilohertz (kHz) up to about 300 billion hertz, or 300 gigahertz (GHz).