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李健一 경북대학교 공과대학 1977 工大硏究誌 Vol.6 No.-
A high reliable line connected first 0 telephone dial pulses dector has been designed with CMOS integrated circuits to control the DDD telephone system.
李健一,李德東 慶北大學校 1975 論文集 Vol.20 No.-
(Ag_xCu_(1-x))_2HgI_4 (0≤x≤1) CTR thermistors were fabricated and their electrical characteristics were investigated. The x-dependent critical temperatures were in the range of (45∼75)℃. The x=0.9 samples gave the highest resistance anomaly index, 3.
李健一,宋奎翼 경북대학교 공과대학 1976 工大硏究誌 Vol.5 No.-
The telephone-number-digital-display-circuit is designed, which picks up initially a signal from dial pulses with little effect on telephone and can finally display the successive dial numbers on LED display unit up to 10 digits. The dynamic display system and TTL IC were used to simplify wiring and the number of logic gates, and to improve the performance respectively. This circuit was high reliable in the temperature range of 0°―70℃. It can be used to monitor dialing numbers to give confidence to subscribers, to test misconnecting troubles in telephone exchange offices, to inspect a complete dial set in a factories manufacturing the telephone set.
李建一,崔文奭 慶北大學校 1976 論文集 Vol.22 No.-
A low cost and dfficient trasformer-less SCR regulator has been developed on the basis of J.Hicks and A.Hopengarten's circuit by the method of replacing the dc feedback circuit with an ac feedback circuit. The improved circuit can also work in full-wave instead of their half-wave operation. A simple constant voltage circuit employing the avalanche diode has been added for the reference voltage. The regulated dc output voltage range has been from 15 to 80 volts for the current up to about 1.5 amperes and its line regulation can be good as one percent over the range from 15 to 40 volts.
出力電壓과 內部抵抗의 可變이 서로 獨立的인 內部抵抗可變 直流安定化電源
李健一 경북대학교 공과대학 1977 工大硏究誌 Vol.6 No.-
In this work, we have designed dc regulated power supply with variable internal resistance where output open circuit voltage and internal resistance are independently varied each other. The electrical characteristics observed in this power supply can be outlined as following: 1) Internal resistance can be varied equivalently in wide ranges from 0.2 to 500 ohms, 2) practically no vriation (within 0.02 percent per volt) is observed in output open circuit voltage when the internal resistance is varied, and 3) practically no variation (within 0.05 percent per ohm) is observed in internal resistance when the output open circuit voltage is varied.
李健一 경북대학교 공과대학 1976 工大硏究誌 Vol.5 No.-
A simple and high reliable first 0 telephone number detector is designed to control the DDD telephone system.
Ρ-n接合에 있어서의 Avalanche Breakdown의 遲延時間
李宇一,孫炳基,李健一 慶北大學校 1970 論文集 Vol.14 No.-
The fluctuation of current pulse delay time in the onset of the avalanche breakdown of p-n junctions after the application of a step voltage has been investigated. The pulse counting rate R for the delay time t is expressed in terms of the trapped carrier density, the detrapping time, the activation energy of the trap, temperature, and illumination. The theory predicts the linearity between In R and t provided that the temperature and illumination of the junction are kept constant. The prediction was in good agreement with experimental results.
曺海晟,李健一 경북대학교 공과대학 1977 工大硏究誌 Vol.6 No.-
A high reliable and useful digital telephone-dial tester has been disigned, which can be used at the telephone exchange office laboratories and telephone set manufacturing factories by testing the dial impulse number, make rate of impulse and dial return time.
스위치 커패시터 位相固定回路를 利用한 周波數合成方式의 텔레비젼 選局回路
文光碩,李健一 경북대학교 공과대학 1984 工大硏究誌 Vol.13 No.-
In this paper, a television-channel selection circuits using SC-PLL was designed and interface circuits for the microprocessor was provided. The circuit has employed one-touch channel selection method and sequential channel selection method. The tuning speeds of the system in FCC normal channels were about 0.3 sec. Overall experimental circuits of this paper can be implemented one-chip IC.
朴成漢,李健一 경북대학교 공과대학 1974 工大硏究誌 Vol.3 No.-
Nagata's negative resistance circuit, which consists of complementary transistors, presents wide-range linear and stable negative resistance characteristics. These characteristics are controlled by the choice of a resistor and indepependent of transistor parameters. The i-ν characteristic of this circuit is an S-curve and is very similar to that of SCR. The peak input voltage of the circuit is controlled by the load resirtor R_c of the first transistor, and the trigger current to the base of the first transistor. It increases linearly with the log (1/R_c) and the trigger current.