in fig1 block 10 represents a microphone which is mounted into the head of the stethoscope . the microphone in response to korotkoff sounds initiates a signal . the microphone in a preferred embodiment would be incorporated into the housing of the head of the stethoscope . the signal is fed into an amplifier , block 12 , which boosts the signal about fifty times . the amplified signal is then input to block 14 , a voltage comparator which compares the signal voltage to a reference voltage . if the signal voltage is greater than the reference voltage , the electrical signal passes . the output of block 14 is connected to block 16 which elongates the signal in duration . the output of block 16 is connected to the inputs of blocks 18 and 20 . the counter in block 18 sends an off switch signal to block 20 with each received signal until the operator presses the actuator button block 22 . at this point block 18 sends an on signal for each received signal to block 20 . the counter in block 18 allows a set number of such signals to pass until it again turns the switch to the off position . the switch remains off until the start button , block 22 , is pushed again . the pulse counter block , block 24 , calculates the pulse by starting a timer when the first signal is received . the timer is then stopped after the set number of pulses is received and places the resultant elapsed time into the equation x ( depending on the set number of signals ) divided by the time measured equals the pulse rate per minute . the pulse rate per minute is then sent to a display , block 26 . in fig2 a preferred embodiment is diagrammed showing the stethoscope head and housing 32 with a digital display 34 , preferably an lcd , and an actuator button 36 with flexible tubing 30 and ear pieces 28 . referring now to fig3 a close up of the stethoscope head and housing 32 is shown with the digital display 34 , actuator button 36 in convenient location for one handed usage , diaphragm annulus 40 to secure the diaphragm to the head , and tubing 30 . fig4 is a cross - section of fig3 with the digital display 34 , the actuator button 36 , diaphragm 38 , diaphragm annulus 40 , microphone transducer 42 , and one or more circuit boards 44 located directly beneath the lcd display . the operation of the apparatus of the invention will be readily understood from the following description of its use . starting with the use of a sphygmomanometer , the observer will inflate the air cuff which has been wrapped about the patient &# 39 ; s extremity in the process of taking the blood pressure . the stethoscope head 32 is pressed against the inner aspect of the volar side of the antecubital space where the brachial artery lies as the observer listens with the ear pieces 28 and tubing 30 . the air will be slowly released from the air cuff and the korotkoff sounds will be heard by the observer . with the first loud korotkoff sound the actuator button 36 will be pushed and the apparatus thus described will respond to the sounds . as the observer completes taking the blood pressure by further release of pressure in the air cuff , the apparatus will read out a pulse so obtained . those skilled in the art will recognize that an audible or visual signal of the electrical signal corresponding to the korotkoff sounds would be advantageous as a means of allowing the observer to become the monitor for judging the accuracy of the device . those skilled in the art will also note that it would be advantageous to also have watch functions including a timer , alarm , 24 hour clock functions , and seconds display . it is obvious for one skilled in the art that numerous modifications may be made to the apparatus of the invention concerning for example the type of stethoscope , the manner of processing the signal , the manner of counting and calculating the results , the manner in which the pulse rate be electronically monitored , without departing from the scope of the invention . a quality control circuit could be added to the invention in which an irregular pulse rate could set off an alarm to notify the observer of this irregularity . consequently , the invention should not be interpreted as being limited to the particular embodiment described here , it covers on the contrary all variants thereof .
a miniaturized electronic stethoscope designed to be used in conjunction with a standard sphygmomanometer in the measurement of blood pressure and pulse rate simultaneously in which a transducer converts the korotkoff sounds into electrical signals . the electrical signals are amplified and fed to a counter in which the detected pulse rate per unit time is calculated and then the result is displayed as a digital pulse rate .