Abstract: An anti-copy system which prevents copying of tapes and records and other source material by placing a degrade signal on an analog source signal to be recorded on a recording device. One embodiment of the system includes a pulse width modulation (PWM) circuit that generates a pulsed signal in a frequency range from near the upper end to well above the range of hearing. The PWM pulsed signal is modulated by the source signal to be recorded. The PWM signal becomes the degrade signal. This degrade signal is keyed so that it is combined with the source signal only when the frequency of the source signal exceeds a desired threshold. The combined source signal and degrade signal are recorded on the original recording. This original recording can be played back without the presence of the degrade signal impacting the audible quality of the reproduced source signal.

Abstract: An audio processor which converts monaural input to a realistic pleasant sounding binaural output in which optical coupling means, having a nonlinear transfer characteristic, creates an unbalanced output to a pair of audio outputs. The system provides for a high or low level input, which may be selected by a switch, to an emitter follower which drives an optical coupling circuit. The optical coupling circuit is comprised of a light emitting diode and a phototransistor connected in a phase splitting network. The phase splitting network provides an unbalanced output to terminals for connecting to preamplifiers, amplifiers, etc. An alternative embodiment employs two optical coupling circuits in two separate signal processing channels, including two phase splitting networks.