recording or playback of information by relative movement between a record track and a transducer, the transducer directly producing, or being directly actuated by, modulation in the track being recorded or played-back, and the extent of modulation corresponding to the signal being recorded or played-back;
apparatus and machines for recording or playback, and parts thereof, such as heads;
record carriers for use with such apparatus and machines;
associated working of other apparatus with such apparatus and machines.
In this subclass, the following terms or expressions are used with the meanings indicated:
"head" includes any means for converting sinusoidal or non-sinusoidal electric wave-forms into variations of the physical condition of at least the adjacent surface of the record carrier, or vice versa;
"record carrier" means a body, such as a cylinder, disc, card, tape, or wire, capable of permanently holding information, which can be read-off by a sensing element movable relatively to the record carrier.