Abstract: A low cost diagnostic system for testing the airborne static discharge systems and the grounding systems for aircraft. The present invention is a passive electrostatic detection scheme comprising an array of inexpensive, miniaturized sensors for measuring the detected E-field disturbances from aircraft. The measurements are taken on the runway upon arrival and indicate whether the aircraft had an appreciable accumulated charge indicating a failure of the electrostatic discharge system. The system further verifies that the ground discharge devices are properly working and any charge is dissipated upon landing. In one embodiment the measurement information is transmitted to a central location where the aircraft and the measurement data are matched and maintenance is scheduled for aircraft having high levels of electrostatic charge.

Abstract: In a data encrypting/decrypting system both the encoding and decoding stations are receptive of a common source of time varying digital signals. The digital signals in the encoding station are applied to one or both of circuits for encrypting data supplied to the encoding station and spreading the spectrum of a carrier which is modulated by the encrypted data. The digital signals in the decoding station are applied to one or both of circuits for despreading the carrier transmitted by the encoding station and decrypting the received encrypted data. In the decoding station and optionally in the encoding station delays are interposed between the circuits therein and the reception point of the digital signals of values such that the digital signals arrive at the decoding station circuit(s) in synchronism with when data encoded in accordance with a particular digital signal arrives at the decoding station.

Abstract: A vehicle identification system includes a doppler radar producing a doppler frequency signal having noise components and having a value f.sub.D corresponding to the speed of the vehicle to be identified and a doppler frequency having a value X.multidot.f.sub.D corresponding to the speed of the vehicle propelling means, each doppler frequency being modulated by signals corresponding to the movements made by individual elements of the vehicle propelling means. The doppler signal is passed through first and second adjustable filters adjusted to pass f.sub.D and x.multidot.f.sub.D respectively and sidebands relating to the modulating signal. Amplitude detectors coupled to the outputs of the two filters remove the doppler frequencies leaving the modulating signals relating to the movement of the vehicle elements. The modulating signals are applied to an adjustable commutating filter adjusted to frequency by a signal corresponding to frequency f.sub.D.

Abstract: A commutating filter circuit producing only the fundamental frequency and odd harmonics of an input signal comprises first and second commutating filters each connected to receive the input signal and coupled to pass an output signal to the non-inverting and inverting terminals, respectively, of a differential amplifier. The first filter comprises N stages, each having a time constant of RC and a filter sampling frequency of f.sub.1. The second filter comprises N/2 stages, each having a time constant of 2RC and a filter sampling frequency of 2f.sub.1. The resultant signal from the differential amplifier contains only the fundamental frequencies and odd harmonics of the input signal.

Abstract: An FM transmitter linearity test equipment includes an amplitude modulation generator signal source producing an amplitude modulated signal of known varying amplitudes changing at a known rate and a demodulator for demodulating the resulting frequency FM signal from the transmitter. The test equipment also includes a commutating filter operating at said known rate and which is receptive of the demodulated signal for producing a signal of varying amplitude which is compared with the signal produced by the signal source to determine the linearity of the FM transmitter.

Abstract: Method and apparatus for separating dispersed multi-phase, fluid systems by flowing a gaseous medium through a liquid phase in a plurality of substantially vertical conduit members positioned over a manifold member through which the gas is supplied; and removing the separated phases from the predominant liquid. The components to be separated may be dispersed in the liquid or the gas.Flow of the gas through the conduit exposes the system to a large effective surface area as well as carrying the lighter components to the surface to form a separate, continuous phase, and inducing the heavier, usually solid, components to settle to the bottom of the apparatus. Optionally, particles may be included in the system to further increase the effective surface area.

Abstract: Method and apparatus for purifying water or treating waste water by utilizing a gaseous medium, and particularly oxygen or air, to lift the water through a biological reactor in the form of a plurality of substantially vertical conduit members positioned over a manifold member through which the gas is supplied to the conduit. Preferably, when pure oxygen is employed, the system is sealed and utilizes a carbon dioxide absorber. Optionally, particles may be included in the water being treated.

Abstract: A tracking band-pass filter useful for locking onto, and passing, an input signal which changes rapidly in frequency. The filter has a frequency pass band controlled by a rectangular voltage waveform which is derived from the output signal passed by the filter. The filter output signal is translated from a sine wave to a pulse wave. The period between each two successive pulses is measured by counting the cycles of an oscillator during each respective period. The time-representing count is inverted to a frequency-representing count which controls the duty cycle of a rectangular wave used to make the filter track the changing frequency of the input signal.

Abstract: A circuit for generating a clean square electrical pulse having a duration equal to the spark zone duration in an internal combustion engine includes a comparator connected to produce an output when the signal input thereto, coupled from the primary winding of the ignition coil, exceeds a predetermined high voltage at the reference voltage input of the comparator. A one-shot multivibrator triggered by the initial output of the comparator generates an output continuing beyond the duration of high voltage ringing in the signal from the ignition coil. A "nor" gate receptive to outputs from the comparator and the one-shot produces an output which reduces the reference voltage applied to the comparator to a value below the plateau of the signal from the ignition coil. The "nor" gate provides the desired output spark zone duration pulse.