Abstract: A gated oscillator is coupled to a set of headphones through a connector interposed between the headphone plug and a mating jack in a stereo receiver or other source of audio information. An acoustic pickup is coupled to the oscillator through circuitry which establishes a threshold for the oscillator. When a sound sufficiently loud to exceed a threshold is detected by the pickup, the oscillator is actuated and superimposes an audible tone on the audio information.

Abstract: A pattern recognition system includes a magnetic core correlator which is used for recognizing a pattern being scanned. A bit train of digital signals, describing the input image, is applied to a plurality of serially connected shift registers so that a train of pulses is stored in the shift registers. Selected bit positions from certain of the shift registers are connected to drivers which drive an array of magnetic cores with flux changes in a pattern corresponding with the stored input image. The array of magnetic cores has a group of sense lines, one sense line for each of the different patterns to be recognized. Each sense line has a winding on selected cores with the windings connected in series. Certain of the windings on a given sense line are aiding and the remaining windings are opposing so that the pattern of flux changes in the cores creates voltages on the windings which are additive when signals closely representing the pattern being recognized are applied to said drivers.