Antenna is an element, which effectively radiates or absorbs the radio wave. Roughly speaking, if we send an oscillating current (alternate current) into the antenna, waves of electric and magnetic fields (electromagnetic wave) are produced and emitted. If, on the other hand, the antenna receives an electromagnetic wave, the altenate current is induced in the antenna. Left: TV antenna (Photo by Yukiko Tajima)

	Receiver is a device, which changes radio signals into electric signals, and eventually transforms them into voice. Receiver is made of various circuits. One of them is a simple straight receiver, shown below.