3872251 is referenced by 38 patents and cites 7 patents.

Described is a portable, battery-operated electrocardiography (EKG) transmitter, and method of transmission, from the patient's location via telephone lines to a diagnostic central. The transmitter, which includes a 'calibration'-signal generator for producing a reference signal, an EKG-signal amplifier and a frequency-modulator, operates at a nominal carrier frequency of 1800 HZ. Each (periodic or emergency) transmission commences with a sequence of calibrate-signal square waves at about 5 Hz for about 5 seconds. The calibrate signals modulate the 1800 Hz carrier to produce a 225 Hz deviation and deflect the EKG recording pen at the diagnostic central by 1 cm. The diagnostic central maintains a fixed sensitivity of 1 cm deflection per 225 Hz=.DELTA.f as a reference signal for all patients. At the end of the 5 second interval, the calibration signal generation terminates automatically, and then the amplified EKG-signals are switched to modulate the carrier. The reference signal, as pen-recorded preceding and juxtaposed to the recorded EKG-signals proper, serves to provide: (1) a convenient visual reference and an accurate calibration marker for the EKG-signal amplitudes, to indicate changes in EKG signals relative to previous transmissions; (2) a basis for discrimination between changes attributable to physiological changes in the patient and changes attributable to aging and drift of transmitter components; (3) a forecast of failure of a patient's pacemaker; (4) early warning of the approach of end of the battery life. However, long battery and low drift are assured by automatic shut-off of the transmitter after operational use thereof for about 90 seconds maximum, and by selection of stable components.

Electrocardiography transmitter and transmission method
Application Number
Publication Number
Application Date
February 20, 1973
Publication Date
March 18, 1975
Steinberg Sidney
Katz George M
Auerbach Albert A
Yuter & Rosen
Medalert Corporation
H04m 11/00
A61B 05/00
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