Sounds from two directions
Stereophonic sound helps to give a sense of direction and feeling of depth to radio broadcasts or recordings. When you hear an orchestra playing on the radio, for example, you can tell where the violins, woodwind and drums are positioned.
Many VHF radio programmes are now broadcast in stereophonic sound - a system pioneered in the United States by Zenith and General Electric in 1961. The programme is recorded using a number of microphones, and edited to produce sounds from the right and left of the broadcast studio on two separate tracks.
The transmitter sends out two sets of radio signals over the air. One set carries the combined output of the microphones so that it can be received on ordinary (mono) receivers. The other set carries coded signals for a stereo receiver. It has a decoder that can sort out the coded set into left and right channel signals. These are amplified separately, and fed to separate left-hand and right-hand loudspeakers.