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.
A transmitter comprising: first means for generating a subcarrier signal at a first frequency; second means connected to said first means for modulating the subcarrier signal with an input signal; third means connected to said second means for producing a carrier signal at a second frequency modulated by the inputmodulated subcarrier signal; input means connected to said second means for conveying an input signal to the second means; output means having an antenna connected to said third means for radiating the modulated carrier signal; supply means connected for supplying power to the transmitter; detection means connected to said supply means for detecting a decrease in the voltage ouput of the supply means below a given value; and fault means connected to said detection means for preventing radiation of the carrier signal when the voltage output of the supply means falls below said given value.
Claim 2
Dependent Claim
144 words
A transmitter comprising: first means for generating a subcarrier signal at a first frequency; second means connected to said first means for modulating the subcarrier signal with an input signal; third means connected to said second means for producing a carrier signal at a second frequency modulated by the inputmodulated subcarrier signal; input means connected to said second means for conveying an input signal to the second means; output means having an antenna connected to said third means for radiating the modulated carrier signal; supply means connected for supplying power to the transmitter; detection means connected to said supply means for detecting a decrease in the voltage ouput of the supply means below a given value; and fault means connected to said detection means for preventing radiation of the carrier signal when the voltage output of the supply means falls below said given value.
Claim 3
Dependent Claim
56 words
A transmitter as in claim 1 wherein: the supply means includes a regulator having a series pass transistor, said transistor having two terminals that form a circuit for passing the supply means output current and a base terminal for controlling said current; and the detection means monitors the current in the base terminal of the transistor.