ELECTROCARDIOGRAPH TELEMETRY SYSTEM HAVING CIRCUITRY FOR INDICATING INOPERATIVE CONDITIONS

• US 3,768,017 A
• Filed: 12/14/1971
• Issued: 10/23/1973
• Est. Priority Date: 12/14/1971
• Status: Expired due to Term

• Current Assignee: Alfred M. Nardizzi, James L. Larsen, Richard F. Dillman
• Original Assignee: Alfred M. Nardizzi, James L. Larsen, Richard F. Dillman
• Inventors: Dillman, Richard F., Larsen, James L., Nardizzi, Alfred M.
• Primary Examiner(s): Mayer, Albert J.
• Application Number:
  US05/207,859
• Time in Patent Office: 679 Days
• Field of Search: 128/2R,2.6R.2.1A 325/48,45,344,348,349,478,346,417,418-420,423
• US Class Current: 455/45
• CPC Class Codes: A61B 5/0006 ECG or EEG signals
• CPC Class Codes: A61B 5/276 Protection against electrode failure
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61B 5/33 specially adapted for cooperation with other devices
• CPC Class Codes: Y10S 128/903 Radio telemetry

Abstract

Special circuitry in the transmitter of an electrocardiograph (ECG) telemetry system detects various malfunctions of the system and changes the transmitted signal to indicate their presence to the system receiver. When the transmitter detects that an input electrode has become detached from the patient, it changes the frequency of the subcarrier signal to indicate this problem to the receiver. The receiver monitors the subcarrier frequency and flashes an alarm light when the frequency corresponds to the electrode inoperative condition. When the voltage output from an aging battery becomes too low to adequately energize the transmitter, special circuitry stops the transmission of signals from the transmitter. When the receiver cannot detect a transmitted signal, it indicates that either the battery needs replacement or the transmitter is out of range.

Claims

1. A system for wireless transmission of electrical signals, comprising:

an input circuit having an electrode for receiving an input signal applied thereto;

transmitter means including frequency-control means connected to said input circuit for radiating an output signal that is modulated by a subcarrier signal means which is modulated within a preselected band of frequencies by an input signal applied to said electrode, and means for radiating said output signal modulated by a said subcarrier signal having a signal frequency outside the limits of said band in response to an open-circuit electrode of the input circuit;

reception means including a demodulator adapted to receive the radiated output signal for producing said subcarrier signal therefrom; and

detector means connected to said reception means for producing a first output indicative of reception of the radiated output signal modulated by said signal frequency.

2. A system as in claim 1 wherein:

said reception means includes first and second detectors, each connected to receive the demodulated subcarrier signal, the first detector producing therefrom a first signal representative of the peak amplitudes of said subcarrier signal over a given first time interval and said second detector producing therefrom a second signal representative of the peak amplitudes of said subcarrier signal over a given second time interval which is shorter than said first time interval; and

comprising comparator means operable for comparing applied signals with a pair of signal levels, said comparator means being connected to said first and second detectors for producing a second output indicative of an inoperative condition in response to the first signal from the first detector attaining a value greater than a first one of said pair of signal levels and the second signal from the second detector attaining a value less than a second one of said pair of signal levels.

3. A system as in claim 2 wherein:

the transmitter means includes an FM-FM radio wave transmitter having an electrode of said input circuit adapted to be attached to the body of a patient for receiving an input signal therefrom;

said frequency-control means sets the signal frequency of said subcarrier signal to a frequency lower than the frequencies of said band in response to an electrode detaching from the body of a patient; and

logic means connected to said comparator means and to said detector means for inhibiting the first output indicative of reception of the radiated output signal modulated by said signal frequency in response to said second output produced by said comparator means.

4. A system as in claim 1 wherein said reception means also produces an information signal from said subcarrier signal which is representative of said input signal;

and comprising inhibit means connected to said reception means for inhibiting said information signal from the reception means in response to said first output from said detector means.

5. A receiver comprising:

reception means for detecting radiated electrical signals;

first means connected to said reception means for demodulating a detected input signaL to produce a subcarrier signal;

second means connected to said first means for demodulating the subcarrier signal to produce an information signal;

output means connected to said second means for deriving the information signal from the receiver;

a first detector connected to said first means for converting the peak amplitude of the subcarrier signal over a given first time interval to a representative first D.C. signal;

a second detector connected to said first means that converts the peak amplitude of the subcarrier signal over a given second time interval to a representative second D.C. signal, said first time interval being longer than said second time interval; and

comparator means operable for comparing applied signals with a pair of signal levels;

said comparator means being connected to said first and second detectors for producing an output indication of an inoperative condition in response to the first D.C. signal of the first detector attaining a value greater than a first one of said pair of signal levels or in response to the second D.C. signal of the second detector attaining a value less than a second one of said pair of signal levels.

6. A receiver as in claim 5 wherein said first means includes a demodulator and a local oscillator signal generator connected thereto;

and comprises circuit means connected to said comparator means and to said signal generator for varying the frequency of the signal produced thereby in response to the output indication of an inoperative condition produced by said comparator means.

7. A receiver as in claim 6 comprising logic means connected to said output means and to said comparator means for inhibiting the information signal from the output means in response to the output indication of an inoperative condition produced by said comparator means.