| 摘要 |
1,005,885. Measuring electrically. CHEMETRON CORPORATION. March 23, 1962 [March 23,1961], No.11233/62. Heading G1N. [Also in Division A5]. Cardiac monitoring apparatus comprises an electrically conductive case for attachment to a part of the body to form one electrode and a monitoring circuit in the case and connected between the case and a terminal for a second electrode, the monitoring circuit including a power supply 19, an amplifier 20, 35, 50 and decoupling means for preventing load surges from affecting the power supply, said decoupling means comprising a capacitor 74 in parallel with the power supply. The circuit including a speaker 82 and/or an indicator lamp (not shown) is contained in the casing. The amplifier comprises three stages including transistors 21, 36, 51. The first stage includes high frequency attenuation means comprising a capacitor 30 and a resistor 26 in a negative feed-back circuit. A capacitor 33 in the amplifier input prevents D.C. leakage through the body affecting the transistor base of the first stage. A resistor-capacitor part 48, 49 decouples the battery from the first two amplifier stages. The output of the second stage is modified by an integrating capacitor 46 to extend the time base of the final signal. The amplifier output is supplied through a plug and socket connection 63 to either the indicator lamp or to an oscillator 65 which comprises a transistor 66 and is decoupled from the battery by a resistor capacitor pair 73, 74. The oscillator output is coupled to the circuit of the speaker through a transformer 75. The biasing of the transistor 66 is controlled by resistors 83, 84, 85 and a rheostat 86 which is adjusted to produce the required oscillation amplitude by a knob 17 on the casing. The knob also operates an on-off switch 78. A diode 91 diverts any rectified signal appearing on the base of the oscillator transistor.
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