RU45077U1 - OBSTETRIC MONITOR - Google Patents

Abstract

The utility model relates to the field of medicine, namely to obstetrics and relates to devices that serve to control the nature of labor through monitoring. The technical effect to which the claimed utility model aims is to expand the functionality of AM by creating a multi-channel AM, which allows you to implement control functions, such as: measuring and monitoring the fetal CVS according to direct ECM at the time of its birth and the Doppler echocardiogram in the prenatal period, as well as the contractile function of the uterus, which allows to determine the time of occurrence of labor weakness (dystocia) and CCC of the woman in labor The obstetric monitor contains an electrocardiographic channel of the fetus - I and an electro-hysterographic channel of the mother - II, the inputs of which are an electrocardiogram sensor and a uterine contractions sensor, respectively; the fetal echocardiographic channel — III and the mother’s electrocardiographic channel — IV, the inputs of which are an ultrasonic sensor and the electrocardiogram signal, respectively, while the outputs of the fetal electrocardiographic channel — I, the mother’s electrohysterographic channel — II, the fetal echocardiographic channel — III, and the mother’s electrocardiographic channel — IV are connected to computer part of the monitor, which integrally reflects the state of the mother-fetus system. The proposed AM with a simple structural construction and the use of a universal element base allows you to implement the listed control functions. And the acoustic form of the alarm, integrally representing the state of the mother-fetus system, does not take

visual system of the midwife, i.e. does not distract her from visual control of the birth process. 1 n.p. and 4 s.p. formulas, 1 ill.

Description

The utility model relates to the field of medicine, namely to obstetrics and relates to devices that serve to control the nature of labor through monitoring.

A device for recording the heart rate (HR) of the fetus during fetal development (ed. St. No. 1022700, IPC A 61 5/02 publ. 06/15/83, Bull. No. 8) - [1]. Heart rate is measured by physical contact with the fetus through the anterior abdominal wall of the woman in labor. Physical impact on the fetus is carried out by the supply of a tonal sound signal with a frequency of 800-8000 Hz, an intensity of 95-105 dB for 1-5 s and at the same time affect the woman in labor with broadband noise. The phonocardiograph sensor is installed on the abdomen of a pregnant woman in the place of the maximum fetal heart rate, which is determined using an obstetric stethoscope or a portable heart rate meter. Sensors for recording electrocardiograms are installed on the white line of the abdomen. An indifferent electrode is mounted on the right thigh. First, a phonocardiogram (FCG) and an electrocardiogram (ECG) control record is performed, which includes registration of the fetal heartbeat without sound exposure and allows you to determine the initial heart rate. Control FKG and an ECG record within 5 min. Writing speed not less than 50 mm / s. Then, an audio signal is supplied from the sound generator by means of an emitter. In this case, the emitter is placed on the anterior abdominal wall of the pregnant woman on the projection of the fetal head. There is no radiation to the external environment, since a unidirectional emitter is used, which excludes the pregnant woman's reaction to sound. In addition, in order to exclude the influence of scattered sound, a pregnant woman binaurally via the phones serves broadband noise with an intensity of 69 dB. The duration of the sound signal is 3 s, the frequency is 800 Hz. Sound value

the signal developed in the area of the preceding part is determined using a sound receiver. The sound receiver is fixed in the area of the posterior vaginal fornix. Sound signal affecting the fetus, 95 dB. FCG and ECG are recorded continuously both during exposure to the sound signal and after. Registration of fetal heartbeat after exposure to a sound signal is continued for 10 minutes. According to the recording of FKG and ECG, the fetal heart rate is calculated during the control measurements (before the sound signal) and after. The initial fetal heart rate is determined at randomly selected recording intervals of 2 seconds. If the difference in these measurements is not more than 4 beats / min, it is assumed that the control record is made correctly and the initial fetal heart rate is reliable. Next, determine the heart rate of the fetus after exposure to the fetus with a sound signal. This value is determined in each recording interval equal to 2 s. Counting is carried out until the heart rate reaches a value equal to the original (for approximately 30 s). After that, the difference between the initial heart rate and the heart rate determined after exposure to the sound signal is determined. A change in the fetal heart rate directly indicates its reaction to a sound stimulus and its functional state.

However, this device is limited to monitoring only one state parameter - fetal heart rate, while the state of the woman in labor remains out of sight. The disadvantage is the lack of automatic registration, which reduces the reliability of the measurements.

These shortcomings are eliminated in the monitor (ed. St. No. 1512560, IPC A 61 V 5/02 publ. 1989 Bull. No. 37) - [2], which provides for the simultaneous registration of fetal heart rate and force of uterine contractions.

Registration of fetal heart rate is carried out by ultrasound. The ultrasound transducer is located on the surface of the abdomen of a pregnant woman in the area of the projection of the heart of the fetus, which is determined

at maximum heart rate when moving the transducer over the surface of the pregnant abdomen.

Accepted ultrasound reflected from the fetal heart is received from the receiving plates, amplified by a high-frequency amplifier and then fed to the input of the demodulator, where the frequency of the Doppler increment that occurs at the time of contraction of the fetal heart is extracted. Then this signal, the repetition period of which coincides with the heart rate, is fed to the input of the heart rate meter, the output signal of which, corresponding to the fetal heart rate determined for each heart rate ("instant" value), is fed to the input of the first channel of the recorder. The current value of heart rate of the fetus is recorded on the chart paper tape of the registrar.

If a pregnant woman has contractile activity of the uterus (spontaneous or caused by stimulants) to register these contractions on the pregnant woman’s stomach in the area of the projection of the uterine fundus, for example, using a belt, a force transducer of uterine contractions is installed, providing the conversion of force into an electrical signal. The output signal of the force transducer of the uterine contractions is amplified by a DC amplifier (the average duration of the uterine contraction is 20-30 s) and from its output is fed to the input of the second channel of the recorder.

Thus, the monitor provides simultaneous registration of fetal heart rate, the strength of uterine contractions and increases the reliability of detecting fetal movements due to automatic registration.

However, this version of the monitor also has a number of significant drawbacks: the lack of sound signals, which forces medical personnel to observe the cardiac activity of the fetus and mother, as well as the contractile activity of the uterus only on the monitor screen, which is not always convenient, since auditory delivery is also necessary during complicated births receiving information, which allows to increase the perception efficiency; fetal control

it is carried out only in the womb (in the initial period of childbirth ECG of the fetus is not observed); there is no control of the mother's CCC.

As a prototype, the invention according to ed. St. No. 1461403, IPC A 61 B 5/02 publ. 02/28/89. Bull. No. 8 - [3], which structurally consists of two channels. In this case, the monitor provides, along with graphical recording of the fetal condition, at the same time auditory reception of information about the fetal heart rate and uterine contractions, as well as a violation of the normal fixation of the uterine contractions sensor, while the sound signals vary in frequency, which increases the efficiency of perception of information about the fetal condition in the conditions of the maternity ward, when the attention of medical personnel is focused on the woman in labor, and not on the graphic recorder.

The monitor contains serially connected electrodes, an electrocardiosignal amplifier (EX), an selector R - an EX wave, a heart rate meter, a heart rate indicator and a two-channel recorder, to the second input of which are connected in series a uterine contractions sensor and a DC amplifier, the output of which is connected to the first input connected and second threshold devices, the outputs of which are connected to the inputs of the decoder, as well as series-connected controlled pulse generator, a frequency divider with a variable coefficient dividing factor, low-frequency amplifier and loudspeaker, and the output of the selector R - EX-wave connected to the input of the controlled pulse generator, and the three outputs of the decoder connected to the corresponding control inputs of the frequency divider with a variable division ratio.

The electrocardiogram taken from the electrodes installed in the initial stage of labor after the cervix is sufficiently opened to the prepartum (the scalp of the fetus or the gluteal region) is fed to the input of the EX amplifier. The reinforced electrocardiogram of the fetus is fed to the input of the R-wave selector. From the output of the R-tooth selector, the pulse train is fed to the input of the heart rate meter and to the input of a controlled pulse generator. A controlled pulse generator produces

a series (pack) of pulses, the duration of which is equal to the duration of the pulses generated by the R-tooth selector. The frequency of burst filling pulses is selected in the range of 800-1200 Hz, which ensures the reliability of reception and processing of sound information about the fetal heart rate in accordance with the recommendations of engineering psychology to ensure optimal interaction between man and technology. At the same time, the signal from the output of the fetal heart rate meter, showing the result of measuring this parameter, is fed to the input of the heart rate indicator and to the input of the first channel of the two-channel recorder, where the current value of the fetal heart rate is recorded. The output signal of the uterine contractions, fixed by a belt on the abdomen of the woman in labor in the area of the projection of the fundus of the uterus, is fed to the input of a DC amplifier and amplified to the required level. From the output of the DC amplifier, a signal reflecting the contractile activity of the uterus is fed to the input of the second channel of the two-channel recorder and to the inputs of the first and second threshold devices. The registrar performs simultaneous registration of two indicators - heart rate of the fetus and the strength of the uterine contractions. A visual examination of this record (cardiotocogram) allows you to detect conditions that threaten the health or even the life of the fetus. However, in the conditions of the maternity ward, where the attention of medical personnel is concentrated on the woman in labor, and not on the fetal monitor, the efficiency of perceiving information about the state of the fetus according to the results of graphic registration is significantly reduced. In the monitor, a signal reflecting the contractile activity of the uterus, from the output of the DC amplifier is fed to the inputs of the first and second threshold devices (for example, Schmidt trigger or voltage comparators). The response threshold U _{p1 of the} first threshold device corresponds to the achievement of the normal initial clip of the pilot of the uterine contractions to the stomach of the woman in labor. The response threshold U _{por2 of the} second threshold device corresponds to the occurrence of uterine contractions, which is accompanied by an increase in the output voltage

DC amplifier. If the uterine contractions sensor is correctly fixed on the woman’s belly, the sensor pilot interacts with the mother’s body at which the output voltage of the DC amplifier is in the range from U _por1 to U _por2 . In this case, the first threshold device is triggered and a voltage corresponding to the level of a logical unit is set at its output, and the second threshold device is not triggered and a voltage corresponding to a logic zero level is stored at its output. As a result, the corresponding code is set at the decoder outputs.

The dividing factor of a frequency divider with a variable dividing coefficient is set to four and the pulse repetition rate f _and in the packet supplied to the input of the low-frequency amplifier is reduced by four times. For example, at a frequency f _and = 800-1200 Hz, the sound signal will have a frequency of 200-300 Hz. This frequency of the sound signal is maintained during the entire time the uterus is not contracted (labor pain). With the beginning of uterine contraction, the voltage increases at the output of the DC amplifier, and when U _{p2 is exceeded} at time t _{1, a} second threshold device is triggered. At the output of the second threshold device, a voltage corresponding to logic level 1 is set. As a result, the corresponding code appears on the outputs of the decoder.

The division ratio of the frequency divider changes and becomes equal to 2. The output signal of the frequency divider is fed to the input of the low-frequency amplifier, and from its output to the loudspeaker. The repetition period of sound impulses (packs) corresponds to the heart rate, and the frequency of the sound signal corresponds to the filling frequency of these packs. Thus, during the monitoring of the birth process by the monitor, the tone of the sound signal repeated in the rhythm of the heart contractions of the fetus corresponds to the nature of the contractile activity of the uterus (at the time of contractions of the uterus, the frequency of the sound signal increases compared to the frequency of the sound signal of the heart rhythm of the fetus in the absence of uterine contractions).

The speed of perception of information is also facilitated by the fact that an increase in the frequency of the sound signal of the fetal heart rhythm during uterine contractions is perceived as a sound of increased intensity. The possibility of simultaneous auditory reception of information about heart contractions of the fetus and uterine contractions provides an increase in the efficiency of perception by medical personnel of information reflecting changes in the condition of the fetus. In case of violation of the normal fixation of the uterine contractions sensor, the pilot of the sensor is not pressed against the woman in labor and, as a result, the output signal of the DC amplifier decreases sharply, taking a value below the level of U _por1 (time t ₃ ). In this case, the voltage at the outputs of the first and second threshold devices takes a value corresponding to the level of logical zero. The corresponding code is set at the decoder outputs.

The division ratio of the frequency divider with a variable division ratio is set to unity. The tonality (frequency) of the sound signal of the fetal heartbeat rhythm becomes the highest (equal to f ₁ ), which provides medical personnel with timely information that the registration of contractile activity of the uterus is violated.

Thus, the monitor, providing auditory reception of information, improves the efficiency of perception of information about the state of the fetus.

However, the prototype does not provide the ability to assess (control) the condition of the fetus in the antenatal period, i.e. It has limited functionality, which reduces the effectiveness of its use in monitoring labor.

The technical effect to which the claimed utility model is aimed is to expand the functionality of the obstetric monitor (AM) by creating a multi-channel AM that allows you to implement control functions, such as: measuring and monitoring the fetal CVS according to direct ECS at the time it appears on

light and Doppler echocardiogram in the prenatal period, as well as the contractile function of the uterus, which allows to determine the time of occurrence of labor weakness (dystocia) and CCC of the woman in labor.

The technical effect is achieved by the fact that in the AM containing the electrocardiographic channel of the fetus and the electro-hysterographic channel of the mother, the inputs of which are the electrocardiographic signal sensor and the uterine contractions sensor, respectively, the electroacoustic transducer, new is that it additionally contains the fetal echocardiographic channel and the mother’s electrocardiographic channel, the inputs of which are respectively, an ultrasonic sensor and an electrocardiogram sensor, while the outputs of the electrocardiographic channel la fetal elektrogisterograficheskogo canal mother, fetal echocardiography and ECG channel channel mothers connected to a computer of the monitor, which is integrally reflects the state of "mother-fetus" system.

The fetal electrocardiographic channel contains a serially connected electrocardiographic signal sensor, which is the input of the fetal electrocardiographic channel, an electrocardiographic signal amplifier, R-wave selector, a comparator, a pulse shaper whose output is connected to the computer part of the monitor and to the first input of the voltage-controlled generator, the second and third inputs of which are connected to the output of the master oscillator and the output of the electro-hysterographic channel, respectively, and the output of the generator controlled by voltage through an logic element, OR is connected to an electro-acoustic transducer, while the comparator output via a feedback circuit through a series-connected time relay and a T-wave selector is connected to the second input of the R-tooth selector.

The mother’s electro-hysterographic channel contains a uterine contractions sensor connected in series, which is the input of the mother’s electro-hysterographic channel, the first connected in parallel

and the second threshold device, a decoder, a frequency divider and an amplifier, which is the output of the mother’s electro-hysterographic channel, is connected to the third input of the generator of the fetal voltage-controlled electrocardiographic channel and to the computer part of the monitor.

The fetal echocardiographic channel contains a serially connected ultrasonic sensor, which is the input of the fetal echocardiographic channel, emitter, amplifier, echo transducer, echo signal analyzer, which is the output of the fetal echocardiographic channel, which is connected to the computer part of the monitor.

The mother’s electrocardiographic channel contains a serially connected electrocardiographic signal sensor, which is the input of the mother’s electrocardiographic channel, an amplifier, an R-wave selector, a comparator, a pulse shaper, which is the output of the mother’s electrocardiographic channel and connected to the computer part of the monitor, while the output of the comparator through the feedback circuit through the series connected by a time relay and a G-tooth selector, connected to the second input of the R-tooth selector.

The essence of the utility model is illustrated in figure 1, which shows the structural-functional diagram of AM.

Here:

1 - sensor electrocardiogram (EX) fetus;

2 - input amplifier;

3 - selector R-wave;

4 - a comparator;

5 - time relay;

6 - T-wave selector;

7 - pulse shaper;

8 - sawtooth voltage generator;

9 - voltage controlled generator;

10 is an OR diagram;

11 - electro-acoustic transducer;

12 - sensor uterine contractions;

13 - the first threshold device;

14 - second threshold device;

15 - decoder;

16 - frequency divider;

17 - amplifier;

18 - ultrasonic sensor;

19 - emitter;

20 - amplifier;

21 - echo signal converter;

22 - echo signal analyzer;

23 - mother EX sensor;

24 - amplifier;

25 - selector R-wave;

26 - a comparator;

27 - time relay;

28 - T-wave selector;

29 - pulse shaper;

30 - computer part of the monitor.

The obstetric monitor contains an electrocardiographic channel of the fetus - I, an electrohysterographic channel of the mother - II, an echocardiographic channel of the fetus - III, an electrocardiographic channel of the mother - IV, the outputs of which are connected to the computer part of the monitor 30, which integrally reflects the state of the mother-fetus system.

The fetal electrocardiographic channel (ECG-p) I consists of a series-connected electrocardiographic signal sensor 1, which is the input of the fetal electrocardiographic channel, an electrocardiogram signal amplifier 2, tooth selector 3, comparator 4, pulse shaper 7, the output of which is connected to the computer part of the monitor 30 and to first entry

voltage-controlled generator 9. The second and third inputs of voltage-controlled generator 9 are connected to the output of the master oscillator 8 and to the output of the electro-hysterographic channel, respectively. The output of the generator controlled by voltage 9 through the OR 10 logic element is connected to the electro-acoustic transducer 11. In this case, the output of the comparator 4 via the feedback circuit through the time relay 5 connected in series and the T-wave selector 6 is connected to the second input of the R-wave 3 selector.

The mother’s electro-hysterographic channel (EGG-m) II consists of series-connected uterine contractions 12, which is the input of the mother’s electro-hysterographic channel, parallel to the first and second threshold devices 13, 14, the decoder 15, the frequency divider 16 and the amplifier 17, which is the output of the mother’s electro-hysterographic channel . The output of the amplifier 17 is connected to the third input of the generator controlled by voltage 9 of the fetal electrocardiographic channel and to the computer part of the monitor 30.

The fetal echocardiographic channel (EhKG-p) III consists of a series-connected ultrasonic sensor 18, which is the input of the fetal echocardiographic channel, emitter 19, amplifier 20, echo signal converter 21, echo signal analyzer 22, which is the output of the fetal echocardiographic channel, which is connected to the computer part of the monitor 30 .

The mother’s electrocardiographic channel (ECG-m) IV consists of a series-connected electrocardiographic signal sensor 23, which is the input of the mother’s electrocardiographic channel, amplifier 24, selector R - tooth 25, comparator 26, pulse shaper 29, which is the output of the mother’s electrocardiographic channel and connected to the computer part monitor 30. In this case, the output of the comparator 26 through the feedback circuit through a series-connected time relay 27 and the T-wave selector 28, is connected to the second input of the selector R - the wave 25.

In the inventive obstetric monitor used the method of the reference model, implemented programmatically using the microprocessor introduced into the AM structure. The essence of this method is to monitor the deviation of the state parameters of the mother-fetus system from its mathematical model, which is formed on the basis of diagnostic studies conducted with the woman in labor throughout the pregnancy cycle. This model has a prognostic character, reflecting both the features of the basic physiological systems of the mother and the morphology of her organs. In this case, with the help of an electro-acoustic transducer, which is an element of an alarm, a composite acoustic signal is formed, each of which is differential and determines, respectively, the state of the key systems of the fetus (ECG-p) and mother (EGG-m). But in general, the acoustic signal integrally represents the mother-fetus system. Also important for the perception of alarm is the acoustic form, the advantage of which is that it does not occupy the visual system of the midwife, i.e. does not distract her from visual control of the birth process.

A feature of monitoring the fetal CVS is the need for duplication of the fetal CVC monitoring channel due to its mobility and the need to increase the reliability and safety of the contact of the fetal electrodes during childbirth and in the phases immediately preceding the birth. This is due to the introduction into the structure of AM in addition to the electrocardiographic channel of the echocardiographic channel for monitoring the fetal CVS.

In the AM under consideration, the monitoring of the mother’s condition is also carried out in two channels: electro-hysterographic, which allows determining the moment of labor weakness and, therefore, based on the assessment of the dynamics of the development of this process, apply both physiotherapeutic and pharmacological effects on the woman in labor, as well as electrocardiographic, since at the heart of the successful course of the birth process is the normal work of the cardiovascular system of the woman in childbirth.

The work of AM proceeds as follows.

The electrocardiogram (EX), taken from the electrodes 1, installed in the initial period of labor (the cervical dilatation phase) to the fetal part (the scalp of the fetus or the gluteal region), is fed to the input of the amplifier EX 2. The enhanced fetal EC is fed to the input of the R-tooth selector 3. From the output of the R-tooth selector, the pulse train is transmitted to the input of the comparator 4, at the output of which there is a control signal transmitted simultaneously to the pulse former 7 and in parallel, through the feedback circuit, to the time relay 5, melting according to the principle of a comparator. This leads to the operation of the selector of the G-wave 6, the output signal of which returns the selector R-wave to its original state. This ensures the selection of the R-wave and simultaneously excludes the registration of the T-wave in case of its abnormal level. Such a circuitry solution of the electrocardiographic channel AM increases its noise immunity. The output signal from the pulse shaper 7 enters the computer part of the monitor 30. To facilitate the process of controlling labor activity, the acoustic signal generating circuit, the frequency of which is determined by the electro-hysterographic channel, is introduced into the AM under consideration. This signal is interrupted by short pulses from the fetal electrocardiographic channel.

Structurally, this circuit includes a generator 9, the frequency of which is determined by the voltage supplied from the output of the electro-hysterographic channel AM, and the waveform is determined by the reference sawtooth voltage generator 8. The signals from the output of the pulse shaper 7 and from the output of the generator 9 are fed to the logic element OR 10, which controls the operation electro-acoustic transducer 11. The electro-hysterographic channel circuit includes: uterine contractions 12; first and second threshold devices 13, 14; decoder 15; frequency divider 16; an amplifier 17, and the fetal echocardiographic channel circuit includes: an ultrasonic transducer 18; emitter 19; amplifier 20; echo transducer

21; echo signal analyzer 22. In the circuit of the mother’s electrocardiographic channel: EX sensor 23; amplifier 24; R-wave selector 25; comparator 26; time relay 27; G-wave selector 28; pulse shaper 29.

Thus, the proposed obstetric monitor with a simple structural construction and the use of a universal elemental base allows you to implement such control functions as: measuring and monitoring the fetal CVS according to direct electrocardiogram and Doppler echocardiosignal, as well as the contractile function of the uterus, which allows determining the time of the onset of labor weakness (dystocia ) and the CCC of the woman in childbirth, and the sound alarm, integrally representing the state of the mother-fetus system, allows the obstetrician to not be distracted To the clerical staff on the monitor screen during childbirth and to receive the necessary information about the state of the woman in labor and the fetus in an acoustic form, which is a contrasting visual form of presenting information. The utility model is feasible and workable.

Claims (5)

1. An obstetric monitor containing the electrocardiographic channel of the fetus and the electro-hysterographic channel of the mother, the inputs of which are the sensor of the electrocardiogram and the uterine contractions, respectively, and the outputs of the channels are connected to the computer part of the monitor, an electro-acoustic transducer, characterized in that it further comprises an echocardiographic channel of the fetus and an electrocardiographic channel mothers whose inputs are respectively an ultrasonic sensor and an electrocardiogram sensor, while moves fetal ECG channel, channel elektrogisterograficheskogo mother, echocardiographic and electrocardiographic channel fetus mother channel connected to a computer of the monitor, which is integrally reflects the state of the "mother-fetus" system. 2. The obstetric monitor according to claim 1, characterized in that the fetal electrocardiographic channel contains a serially connected electrocardiographic signal sensor, which is the input of the fetal electrocardiographic channel, an electrocardiographic signal amplifier, R-wave selector, a comparator, pulse shaper, the output of which is connected to the computer part of the monitor and to the first input of the voltage-controlled generator, the second and third inputs of which are connected to the output of the master oscillator and to the output of the electro-hysterographic channel, respectively This is true, and the output of the voltage-controlled generator through the OR logic element is connected to the electro-acoustic transducer, while the comparator output via the feedback circuit through the time relays and the T-wave selector connected in series is connected to the second input of the R-tooth selector. 3. The obstetric monitor according to claim 1, characterized in that the mother’s electro-hysterographic channel contains uterine contractions connected in series, which is the input of the mother’s electro-hysterographic channel, the first and second threshold devices are connected in parallel, the decoder, frequency divider and amplifier, which is the mother’s output of the electro-hysterographic channel to the third input of the generator controlled by the voltage of the electrocardiographic channel of the fetus and to the computer part of the monitor. 4. The obstetric monitor according to claim 1, characterized in that the fetal echocardiographic channel contains a serially connected ultrasonic sensor, which is the input of the fetal echocardiographic channel, emitter, amplifier, echo transducer, echo signal analyzer, which is the output of the fetal echocardiographic channel, which is connected to the computer part of the monitor . 5. The obstetric monitor according to claim 1, characterized in that the mother’s electrocardiographic channel contains a serially connected electrocardiographic signal sensor, which is the input of the mother’s electrocardiographic channel, an amplifier, an R-wave selector, a comparator, a pulse shaper, which is the output of the mother’s electrocardiographic channel and connected to a computer parts of the monitor, while the output of the comparator through the feedback circuit through a series-connected time relay and a T-wave selector, is connected to the second input of the village torus R-wave.