Harvey Hubbell Incorporated

Ambroz K Skrovanek

Mauro L Gaetano

Carl A Evert

Fred E Clark, Jr

Maur L Gaetano

Disclosed is an apparatus having a signal attenuating portion for setting the gain or loss in amplitude of an electrical signal received by the apparatus, and alternatively, provides a gain of unity without a change of setting. The apparatus employs a plurality of switching devices which may be selectively opened and closed to provide the apparatus with a fixed gain of unity and alternatively predetermined losses or gains to the input signals.

Signal attenuating apparatus

A telephone network protective coupler for connecting terminal equipment to a telephone central office by means of a telephone line. The coupler includes two hybrid circuits which are interconnected to form a transmitting path and a receiving path. A power limiter in the transmitting path can be programmed remotely by selection of an external programming resistor without the direct introduction of noise into the transmitting path. The programming feature permits the gain of the transmitting portion of the device to be varied in steps from 0 to -12dB., and the maximum power output to be varied correspondingly in steps from 0 to -12 dBm. in order to arrive at an optimum signal power level of -12dBm. at the central office. The power limiter includes a controller gain amplifier for varying the attenuation of the transmitting path to a.c. signals, a remotely adjustable attenuator connected to a d.c. voltage source, and a gain control circuit connected to the amplifier and to the attenuator and responsive to adjustment of the attenuator for controling the gain of the amplifier. The power limiter further includes a rectifier for rectifying the a.c. signals after passage through the amplifier, and a maximum power control circuit connected to the rectifier and the attenuator and responsive to the adjustment of the attenuator for keeping the ratio of the amplitude of the rectified a.c. signals to the output voltage of the attenuator less than or substantially equal to a fixed constant.

Telephone network protective coupler

An interface unit for a four wire telephone circuit includes an echo suppressor. A filter circuit is connected to the transmit line drop side to detect voice and SF signals and to selectively couple a regenerated SF signal and the voice signal to the line side of the transmit line. A passive filter is selectively coupled to the receive side to attentuate voice echo but bypass SF signals.

Echo suppressor with SF transmission and regeneration

A transmission line having a fixed characteristic impedance, e.g., 600 ohms, is coupled to a receiver through an input transformer working into a very small impedance, e.g., 10 ohms or less. As compared to a conventional arrangement, where an input transformer works into a load nearly as high as the characteristic impedance of the line, the new arrangement has considerably better low frequency response and delay distortion characteristics. The new arrangement permits a much smaller transformer to be used if desired while retaining favorable low frequency response and delay distortion characteristics.

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Bethesda, MD, United States of America

Ambroz K Skrovanek