Abstract:
An unconditionally stable impedance matching network for matching a nonloaded voice frequency transmission line to the standard impedance of a repeater on said line is provided.
Abstract:
A circuit for varying the amplification afforded to a-c signals transmitted through a transmission line in accordance with the a-c losses of that transmission line. Gain control circuitry is provided which varies the magnitude of amplifying voltages and currents inserted into the transmission line in accordance with the a-c losses of that transmission line. The gain control circuitry is comprised of a line resistance sensor which establishes a contol signal which is a function of the a-c losses of the transmission line. This control signal is applied to the remainder of the gain control circuitry to vary the magnitude of voltages and currents inserted into the transmission line in accordance with that control signal. As a result, the gain control circuitry automatically adjusts the gain of a repeater in accordance with each transmission line connected thereto.
Abstract:
A negative impedance repeater for amplification in telephone lines operating at voice frequency comprises two converters, one of them stable with open terminals and the other stable with short-circuited terminals; each converter is loaded by a fixed network of passive impedances chosen according to the characteristic impedance of the line to be amplified, and provided with means, external to the network of passive impedances, for adjusting the feedback, and consequently the conversion ratio. The conversion ratios of the two converters may be varied independently from each other so that in the case of loaded lines their product may be kept always constant and this allows to adjust the repeater gain without modifying its impedance, while for unloaded lines it is possible to obtain that such product increases with a certain law by increasing gain, and this fact causes an equalization at the highest frequencies of the band, which is necessary for this type of lines.
Abstract:
A negative impedance repeater, particularly suited for use with non-loaded metallic transmission facilities, including a bridgedT series-shunt negative impedance gain unit, and an active impedance correcting unit for matching the impedance of the facility to the fixed image impedance of the gain unit. The impedance corrector, which may be modeled as a variable resistor (positive or negative) in series with a variable negative capacitor, is adapted to decrease the impedance of the facility below a predetermined crossover frequency, and increase its impedance above that frequency. The gain unit is arranged to provide a gain vs. frequency characteristic which is sloped to complement the attenuation vs. frequency slope of corrected transmission facilities.