Abstract: An adaptive line noise detection and cancellation system having a baseline wander filter, high and low pass filters, an adaptive line noise canceler and various noise detectors is provided to identify, signal and remove contamination from an ECG signal wherein the ECG signal is conditioned to remove various portions of the ECG signal prior to processing in various noise detectors while minimizing the signal conditioning effect of the filters on the ECG signal and while further providing the operator with the ability to manually or automatically activate the filters and to indicate the status of the filters on a printout or display.

Abstract: A filter system for detecting and removing small amplitude, high frequency signals such as muscle artifact signals is provided. One form of the system includes a baseline wander filter, high and low pass filters, an adaptive line noise canceler and various noise detectors to identify, signal and remove muscle artifact or loose electrode signal contamination from an ECG signal wherein the ECG signal is conditioned to remove various portions of the ECG signal, such as the QRS portion of the ECG signal, prior to processing in various noise detectors while minimizing the signal conditioning effect of the filters on the ECG signal and while further providing the operator with the ability to manually or automatically activate the filters and to indicate the status of the filters on a printout or display.

Abstract: A noise detection system having a baseline wander filter, high and low pass filters, an adaptive line noise canceler and various noise detectors is provided to identify, signal and remove contamination from an ECG signal wherein the ECG signal is conditioned to remove various portions of the ECG signal prior to processing in various noise detectors while minimizing the signal conditioning effect of the filters on the ECG signal.

Abstract: A linear phase high pass filter is disclosed using a slew rate limiter and a linear phase low pass filter in parallel with a delay for removing baseline wander from an ECG signal. The linear phase low pass filter is preferably a digital Infinite Impulse Response (IIR) filter. The slew rate limiter preferably includes a clipper and a unit delay. An input ECG signal is simultaneously presented to a slew rate limiter and IIR low pass filter combination and an electronic delay. Thereafter, the outputs from the slew rate limiter and IIR low pass filter combination and the delay are passed to a summer where the output from the slew rate limiter and the low pass filter is subtracted from the output of the delay to produce the output ECG signal representation. The combination of the output from the slew rate limiter and the low pass filter being subtracted from a delayed input signal produces a high pass filter. The resulting high pass filter has a relatively high -3 dB cutoff frequency of about 0.

Abstract: A device is provided for reducing the number of ECG data sample points presented to a video display system to avoid overwhelming the video display screen with a number of ECG sample points and to present several seconds of data on the screen at the same time. The device ensures that the maximum and minimum values of the original ECG signal are displayed. A collection of consecutive points is broken into sub-groups which are each processed to produce representative amplitude values for each sub-group which representative values are then displayed on the display screen.In the preferred embodiment, the device includes a microprocessor with electronic memory which calculates a representative amplitude value for each sub-group. The representative amplitude value is chosen depending on whether the sub-group contains a local maximum or a minimum in the values of consecutively sampled points or whether the data points of the sub-group are part of a curve leading to a local maximum or minimum.

Abstract: A linear phase high pass filter having a linear phase low pass filter in parallel with an electronic delay means is disclosed to remove baseline wander from an ECG signal. The linear phase low pass filter is preferably a digital Infinite Impulse Response (IIR) filter. An input ECG signal is simultaneously presented to an IIR low pass filter and an electronic delay. The low pass filter passes the low frequency baseline signal while blocking the ECG signal comprised of higher frequency components than the cutoff frequency of the low pass filter. Thereafter, the outputs from the IIR low pass filter and delay are passed to a summer that subtracts the output of the low pass filter from the output of the delay to produce the output of the filter. The combination of the output of a low pass filter being subtracted from a delayed input signal produces a high pass filter. The resulting high pass filter has a -0.3 dB cutoff frequency of about 0.

Abstract: A filter system for removing small amplitude, high frequency signals such as muscle artifact signals from an ECG signal is provided. The filter system includes a low pass filter with variable cutoff frequencies, an electronic delay and a system for detecting the R wave in the ECG signal and determining the variable cutoff frequency in response to the detection of the R wave. A digitized input ECG signal is simultaneously presented to the electronic delay and the system for detecting the R wave. During the portion of the ECG signal exclusive of the QRS complex, the filter is operated at a low cutoff frequency to filter the muscle artifact signals for a maximum smoothing effect. At a time slightly prior to the on set of the QRS complex, the cutoff frequency is rapidly incrementally increased to a higher cutoff frequency to pass the QRS complex with a minimum reduction of amplitude of the QRS signal.

Abstract: The system receives subscriber station address information in the form of dial pulses transmitted from a calling station along a common intercom circuit and selectively accesses a called subscriber station having a corresponding station address in order to produce a call indication ring-out thereat. The system includes a hook condition detector circuit which controls multiple system functions with respect to the on-hook and off-hook status of the calling station, and further includes a dial pulse detector circuit which effects additional control with respect to completion of dialing by the calling station. The system is suitable for use with ten or varying numbers of subscriber stations and may include, for applications having more than ten subscriber stations, appropriate transfer and associated output control circuitry for double digit operation.