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Abstract

A test signal generator for generating signals simulating the signals obtained from the axles of a railroad car, to permit testing of a railroad car brake controller. During testing of the controller for detection of excessive speed difference between the four axles of a railroad car, the output from a variable frequency oscillator is gated to a first one of the four controller input circuits, while the output from a fixed frequency oscillator is gated to the remaining three input circuits. The output frequency of the variable frequency oscillator is changed to simulate an axle signal indicating to the first input circuit a speed different from the speed indicated to the other three input circuits by the fixed frequency oscillator output. This frequency change continues until the controller indicates an excessive speed difference. During testing for rate of deceleration, the output from a voltage controlled oscillator is gated to a first one of the four controller input circuits. During a first interval of time the oscillator output frequency decreases at a first rate, simulating a railroad car axle signal during normal braking. During a second interval of time the oscillator output frequency decreases at a second, higher rate, simulating a railroad car axle signal with abnormal braking, either with slipping or just prior to slipping. A switch determines whether the excessive speed difference simulation or the deceleration simulation is provided. A multiplexer determines which of the four controller input circuits is selected as the first one. During deceleration testing, the controller can operate in an automatic mode in which receipt of a signal from the controller indicating detection of excessive deceleration sequences the multiplexer so that another of the input circuits is selected as the first one and initiates another cycle of operation.

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