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A transistorized spherical polarcardiograph Harding, Patrick John Ronald

Abstract

The design of a two-dimensional polarcardiograph and the use of two such two-dimensional devices to calculate the third polar coordinate together with the circuitry necessary to derive and amplify a set of voltages proportional to the Cartesian coordinates x, y, and z is described. Although the technique used for obtaining the polar coordinates is similar to that used in other instruments, the circuitry is somewhat different. This is dictated in part by the fact that this device is completely transistorized. Both the Frank and RAFE networks are available for the transformation from patient signals to a set of signals proportional to the Cartesian coordinates x, y, and z. Restoration of the base-line at the optimum time during the cardiac cycle is achieved through a system of gated feedback which is activated by a predictor circuit. The predictor is triggered by an automatic trigger selector. A threshold circuit is associated with each angle output in order to set the output to some predetermined value when the input signal level is so small as to make the angle output indeterminate.

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