Abstract: A microphone system including a plurality of sound transducers integrally contained in a single microphone housing, wherein each transducer has a different polar pick-up pattern. The system includes a remote combiner for the symmetrical addition of the output of each transducer into a composite signal of variable pattern. In the illustrated implementation, the system includes an electret microphone capsule having an omnidirectional pick-up pattern, an electret microphone capsule having a cardioid pick-up pattern, and an electret microphone capsule having a hypercardioid pick-up pattern. The capsules each have a mechanical acoustic phase shifting element to produce the desired pick-up patterns and are time aligned in the housing by placing the capsules together at the same location while pointing in the same direction. Each capsule has an independent power supply module and adjustable gain amplifier for the acoustical balancing of the system which is also integrally contained in the microphone housing.

Abstract: A system for monitoring the level of an intelligence-containing audio frequency signal wherein an operator audibly monitors the signal but cannot adequately monitor a visual level indicator. The system utilizes a threshold detector which compares the level of an audio frequency signal to a preselected level and generates a control signal if the audio frequency signal exceeds the threshold. The system further includes a gate which couples a tone to the headphones of the operator in response to generation of the control signal. In an alternative embodiment, if a second threshold is exceeded, the threshold detector generates a second control signal which changes the tone signal frequency.

Abstract: A full duplex microphone communications system permitting simultaneous bi-directional communications for a two conductor shielded microphone cable. A talkback signal is injected by an encoder at one end using a balanced input to transmit a common-mode signal on the two conductors of the microphone cable using the shield as a ground reference. This signal is then decoded at the other end of the cable by decoding circuitry which covers the common-mode talkback signal.

Abstract: A loudspeaker assembly for use outdoors is disclosed. A woofer speaker is secured in a housing for the downward projection of sound through a generally continuous circumferential aperture between the housing and base. A tweeter is mounted coaxially with the woofer for the projection of sound downwardly thereby providing for the omnidirectional projection of sound from the speaker assembly.