Definition:

A phonograph record (or phonodisc or disc) is a round and flat acetate object which has been moulded from a master disc containing an irregular surface which causes sound vibrations that are transferred to the acetate for purpose of reproduction by a needle. The photograph (or record player) is an electronic device that reproduces sound from records.

Recordings Picture Programmed Instruction:

Characteristics:

Discs usually come in 7" ,10", 12" and 16" sizes and play at speeds of 16 2/3, 33 1/3, 45and 78 rpm (revolutions per minute). The most common sizes and speeds of disc recording are illustrated here. It is important to match the correct needle with the correct groove and speed (see illustration). A needle passes over the irregular surface of the grooves in a record. The resulting vibrations are electrically transmitted to an amplifier which converts them to electrical impulses which are in turn fed to a speaker. The speaker converts electrical energy to sound.

A phonograph has two major units: an electronic system and a mechanical system (see illustration). The electrical system contains the pick-up arm, the amplifie and the speaker. The mechanical system includes the turbtable and the motor. The controls most commonly found on the phonograph are: POWER SWITCH (OFF ON) : VOLUME CONTROL : TONE CONTROL.

Records should receive special care to ensure long life and to preserve quality. Follow these suggestions:

1. Handle records by the outer edges to protect the grooves..
2. Handle the needles with care; be sure the proper needle is being used for the groove of the record keep the surface of the needle free from the lint which accumulates.
3. Keep records in their dust jackets when not in use.
4. Store disc flat or vertically on a shelf away from heat , extreme cold, or dampness.
5. Keep the surface of the record free from dirt and lint which clings to the record due to static electricity. A silicone cloth available at record stores, is the best cleaning agent..