Abstract: A shielded electrical connector having an elongated annular housing composed of an electrically insulative material molded so as to form an elongated structure for the connector and at least a portion of a grasp for a user of said connector. The housing defines outside and inside surfaces and front and rear ends for said connector. A contact holding portion composed of an electrically insulative material is positioned inside said annular housing and includes a plurality of electrically conductive signal contacts positioned therein so as to be completely surrounded by, yet spaced a distance away from, the inside surface of the housing. An elongated annular electrically conductive shield having inner and outer sides is insert molded with the housing so as to be disposed between its outside and inside surfaces.

Abstract: A flexible multi-parameter conductor cable having coaxially symmetric elongated zones for signal carrying conductor placement therein, comprising an electrically conductive inner shield defining an electrically shielded inner longitudinal zone symmetrically disposed along and defining a center of said cable for containing at least one of a first type of signal carrying conductor, and an electrically conductive outer shield spaced a given distance symmetrically around said inner shield so as to define an electrically shielded outer longitudinal zone symmetrically disposed about said inner longitudinal zone for containing a plurality of at least a second type of signal carrying insulated conductor arranged in a single layer adjacent one another in said second longitudinal zone, said second type of conductor having an electrically conductive outer jacket in electrical contact with at least said outer shield.

Abstract: A bank of differential amplifier circuits includes specialized circuits to provide multi-channel differencing with a minimum number of active devices such that the differences between pairs of analog input signals, such as available from patient monitoring electrodes, are derived with half the number of active devices normally utilized. In one embodiment, two operational amplifier circuits are used in a differencing channel which functions together to provide differencing, a properly delayed input signal for use in another differencing channel, high input impedance buffering, a low impedance output for each differential amplifier channel, time-coincident, matched outputs for each differential amplifier channel, and with an additional operational amplifier, a DC rejection circuit which does not affect the low output impedance or the differencing function, thereby to eliminate the necessity of providing separate buffers and active delay circuits which can result in the use of twice the number of active devices.

Abstract: The preamplifier comprises amplifying means, the output of which is inverted relative to the input, and a feedback circuit connected from the output to the input of the amplifier so as to provide a perfect integrator which cancels the amplitude variations resulting from changes in tape speed. The impedance of the feedback circuit and the impedance of the signal source extended to the amplifier are such that the output of the amplifier is the integral of the voltage generated in the inductive head over a wide band of frequencies.

Abstract: An input overload protection circuit particularly suited for use with a high impedance differential amplifier having two inputs is provided. The protection circuit prevents the flow of substantially all leakage currents for input signals within the linear operating range of the amplifier, and includes a first and second serial plurality of diode-action clamping means, such as diodes, connected respectively between the first and second input conductors to the amplifier input and a third conductor connected to a reference potential. Driven guard means operate to apply the voltage appearing on the respective first and second input conductors at their junction with the respective first and second clamping means to the respective first and second plurality of clamping means intermediate the respective ends thereof, thereby to substantially prevent leakage current from flowing through the clamping means from the pair of conductors.

Abstract: In cardiac signal processing apparatus, there is provided improved means for suppressing pacer signal artifacts, including both the discharge pulse and the recharge waveform (tail) of such artifact. Rate-limiting circuitry is used to substantially suppress the discharge pulse. However additional circuitry responsive to the detection of a pacer pulse is operative to obtain a measure of the electrical discharge of the discharge portion of the respective pacer pulse and to use such measure to generate a tail suppression signal which, when added to the original signal, substantially cancels the original pacer tail.A feed-back loop is opened by the rate-limiter when a pacer pulse occurs and in turn permits a large signal to be imposed on a threshold-level-type pacer pulse detector for connecting the large signal (pacer pulse) to a capacitor during the discharge portion of the pacer pulse.

Abstract: An improved fast-recovery circuit for ECG amplifiers and the like. The fast-recovery circuit includes threshold responsive circuitry connected in parallel with part of the resistance associated with the integrator in a feedback circuit of the amplifier. The threshold responsive circuitry operates to increase feedback frequency response of the integrator when the normally very low frequency output signal of the amplifier exceeds a certain threshold. The improved circuit prevents the threshold circuitry from responding to pulses or excursions in the output signal of a relatively higher frequency content and which exceed the amplitude threshold for less than a predetermined interval, as for instance caused by pacer spikes, large QRS complexes and the like. Preferably, the improved threshold responsive means comprises transistor means connected across the integrator's resistance and having capacitance means across the base-emitter circuit thereof for inhibiting response to certain short duration signals.

Abstract: A DC isolation amplifier having improved conductive isolation between its input and output. The amplifier includes an input section having a modulator and an output section having a demodulator and an oscillator section. The modulator and demodulator are nonconductively coupled through inductive loops of two closed-loop cores of magnetic material each having windings inductively coupled to the material of their associated core and to the other of the modulator or the demodulator. Additionally, a unitary closed loop winding couples the two cores such that the net EMF induced in the turns of the winding accordingly such that the respective component of the external magnetic field of the turns is substantially normal to the respective plane of each turn of this plurality. Additionally, this unitary loop is twisted between the cores to comprise a twisted pair additionally to minimize the effects from external magnetic fields. In the preferred embodiment, this loop is limited to two turns per core.