Abstract: An audio-visual alarm includes a flashtube and a voltage signal generator for producing and storing voltages sufficient to operate the flashtube. In series with the flashtube and the voltage generator is the coil of an audio alarm, whereby operation of the flashtube also operates the audio alarm. The audio alarm is selected so that its coil will not interfer with the operation of the flashtube.

Abstract: An automatic audible signaling system for use in emergency warning and direction of people in the evacuation of buildings and the like comprises control apparatus at a central station, a plurality of local amplifiers mounted at remote locations, and at least one loudspeaker connected to each amplifier. The control apparatus comprises an audio preamplifier and, coupled to the output thereof, a modulation transformer having a center-tapped secondary to which a DC voltage is applied when it is desired to operate the loudspeakers. This arrangement supplies mixed DC power and low-level audio signal voltage to each of the remote amplifiers and obviates both the use of a high-power amplifier at the central station and the transmission of a high-power audio signal from the central control apparatus to the remote loudspeakers.

Abstract: An audiovisual signaling device including an auditory signaling means, an inductor for energizing the signaling device, and a circuit interruptor in series circuit with the inductor. A flashtube is electrically connected to the inductor and interruptor, and the inductor acts as an electromagnet when a voltage is impressed across the inductor and interruptor. The series circuit is intermittently interrupted by the interruptor, and the flashtube is actuated in response to the decaying magnetic field of the inductor when the circuit is thus interrupted.

Abstract: A grille for protecting a loudspeaker or the like comprises two substantially identical parts, each part being formed with bars defining a plurality of openings. When the two parts are placed together in back-to-back and head-to-toe relation, the openings in one part are out of register with the openings in the other part. This provides a plurality of circuitous paths through the grille for the passage of sound or the like, but there are no straight-line paths through the grille for the passage of vandalizing implements or the like.

Abstract: The transmitter of a fire-alarm audible signaling system permitting selective communications and signaling transmits digital command signals to receiver-drivers respectively positioned in a number of fire zones over a single two-wire or three-wire circuit that also provides power to the receiver-drivers. Each command signal includes a frame bit, a zone designator comprising, say, four bits and a function designator comprising, say, three bits. The frame bit is always a one and is always the first bit of the command signal, and it serves as a reference. A comparator in each receiver-driver compares an identification code proper to that receiver-driver with the zone designator of each command signal, and each receiver-driver responds to the function designator of a command signal to perform the designated function only in case of a match between the zone designator of the same command signal and the identification code for that receiver-driver.