Abstract: A method of and apparatus for recording information from a master medium onto a slave medium. In one embodiment, digital information on a master medium is reproduced and stored at a first rate, typically at real time, in a first high speed digital storage device such as a magnetic disk drive. The digital information stored in the first storage device, when needed, is transferred at a second rate, much higher than the first, to a second digital storage device in which it is stored until it is scheduled for duplication, at which time the digital information is repeatedly played back at a third rate, much higher than the first rate and slower than the second rate, is converted from digital information into analog information and applied to a duplicating device for recording the analog information onto a slave medium.

Abstract: An FM stereophonic broadcasting system incorporating companding of the difference signal in which the broadcast signal includes both the usual difference signal and a compressed version of the difference signal which utilizes, in the transmitter, a circuit for simultaneously compressing the difference signal according to a desired characteristic and modulating the compressed difference signal onto a carrier and, in the receiver, essentially the same circuit for simultaneously demodulating and expanding an incoming compressed difference signal. Simultaneous compression/modulation is achieved by multiplying the difference signal, the carrier signal and a gain control signal, preferably derived from the output signal from the multiplier, for determining the compression characteristic, thereby producing at the output of the multiplier the carrier modulated with the difference signal compressed according to a desired characteristic.