Abstract: A railroad test vehicle extending in a longitudinal direction comprises a measurement axle comprising two flanged wheels rotatable about a measuring axis extending transversely to the longitudinal direction and adapted to run on two track rails. A cross member extends transversely to the longitudinal direction, is vertically spaced from an underside of the vehicle and is affixed thereto. The connection between the measurement axle and the cross member comprises two trunnions transversely spaced from each other and mounted on the cross member, each trunnion defining a clearance with the cross member sufficient to enable the trunnion to be freely tilted to either side of the vehicle about an axis extending in the longitudinal direction, a support frame mounted on each trunnion for pivoting freely about an axis extending perpendicularly to the longitudinal direction, and two pairs of linkages, the pairs being transversely spaced from each other by the same distance as the transversely spaced trunnions.

Abstract: A general purpose modular acoustic signal generator includes an outer casing unit having a plurality of disengageably connected sections and an insert unit removably positioned in that outer casing unit. The insert unit has a piezoelectric acoustic generator disc mounted thereon and defines a Helmholtz resonator on each side of the acoustic generator disc. A single outer casing is usable with a plurality of different insert units so a single outer casing unit can be associated with a plurality of different Helmholtz resonators.

Abstract: The coded acoustic alarm transmitter/receiver system includes a transmitter for selectively providing both an audible alarm in the audio frequency range and a silent alarm in the ultrasonic frequency range. These alarm signals may be provided by a plurality of signals of different frequencies transmitted simultaneously in either the audio or ultrasonic frequency ranges. Receiver units are tuned to receive specific frequencies from a specific transmitter or group of transmitters.

Abstract: The personal acoustic alarm unit produces an audible alarm signal in the audio range to alert persons in the area of the signal transmitter. This audio alarm signal is formed by a plurality of simultaneously generated audio frequency sonic signals, each of which has a different audio frequency. Receiver units are turned to receive the audio frequency sonic signals from a specific transmitter or group of transmitters.