Abstract: A multiple program input audio system including a plurality of input channels each adapted to provide an output program signal. Each channel comprises an actuator which compares a rectified program signal with a reference signal and generates an actuator output signal when the rectified signal is greater than the reference signal. A zero crossing detector also receives the program signal and generates an initiator pulse when the voltage of the program signal is zero. A master control switch receives the actuator output signal and generates a first master control output signal when pulsed by the initiator pulse and generates a second master control output signal when no signal is received from the actuator. A program switch receives the program signal and in response to the first master control output signal applies the program signal to an audio program buss where the program signals from all the channels are summed and applied to a digital attenuator.

Abstract: A high fidelity loudspeaker system involving a multidriver, semi-omnidirectional, full range, electrodynamic loudspeaker including two, separate but complementary, closed box-like enclosures, an upper unit containing an array of mid-range speakers around three sides and a lower unit containing arrays of low and high frequency speakers around three sides. The low frequency speakers (woofers) on their interior sides include a series of tubes opening into the closed interior of the speaker enclosure, having various lengths in accordance with certain relative, locational relationships. Although the low and high frequency speakers include a single crossover frequency circuit, the "mid-range" speakers are not included in any crossover network but are driven throughout the total frequency input range, although a capacitor can be included to cut off the very low frequencies to the mid-range speakers.