Abstract: A chest drainage device is provided for draining fluid and gases from the pleural cavity of a patient. The drainage device has three chambers; a collection chamber, a water seal chamber, and suction control chamber. The suction control chamber includes a first column which has an upper end adapted to be open to the atmosphere, and a second column, which has a substantially larger cross-sectional area than the first column. A filter member on the lower end of the first column disperses the atmospheric air into small diameter bubbles as it enters liquid present in the lower end of the second column. The present invention provides an improved means for muffling the sound of the atmospheric air as it bubbles through the liquid in the second column. Additionally, the present invention provides a means for increasing the accuracy of the vacuum pressure actually being applied to the pleural cavity of the patient as compared to the prescribed vacuum pressure.

Abstract: A digital noise generator for use in aeroengine noise testing can accurately and repeatably reproduce a standard noise spectrum so that differing noise analysis systems can be calibrated to a common standard. The noise generator comprises a pseudo-random binary sequence generator which is fed with a low clock frequency derived from a high frequency crystal oscillator. The generator produces a pseudo-random noise single bit signal which is fed to the most significant bit input of a digital to analogue converter, whose other inputs are fed with simulated tone data residing within an EPROM, the pseudo-random and tone noise thereby being digitally summed before conversion to an output analogue signal of desired spectral characteristics.

Abstract: A signal processor for use in association with a frequency analyzer, can operate in the frequency translation mode or the filter mode.The signal processor comprises a first low pass filter, the signal from which is fed to two first parallel programmable gain amplifiers controlled by a first digital function controller. The signals then pass via two, second low pass filters to two second programmable gain amplifiers controlled by a second digital function controller. The signals from the second amplifiers are then added by an adder and filtered by a third low pass filter.The first controller is controlled by a frequency signal equal to the frequency in the middle of the bandwidth being translated and the first filter is controlled by a frequency which is a multiple of the control frequency to the first controller.