American Telephone & Telegraph Co., At&t Bell Laboratories

Bell Telephone Laboratories

Oak Industries, Inc.

Howard F Jirka

Pieter Den Toonder

Graham S Stubbs

Johannes C Seltenrijch

Pieter J Fondse

A multifilar transformer apparatus and winding method where first and second windings are bifilar wound around a core for NA turns, the first, second, third, and fourth windings are quadfilar wound around the core for NB turns, and the first and second windings are again bifilar wound around the core for NC turns. Winding symmetry is preserved and a turns ration of (NA+NB+NC):2NB is achieved.

Multifilar transformer apparatus and winding method

A substantial reduction in the common-mode noise generated by a switching-mode power converter is achieved by incorporating a multifilar-wound transformer into the converter in such manner that the inter-winding capacitances cause a cancellation of common-mode, noise components at the converter output.

Floating battery feed circuit using multifilar transformer

A floating, constant power, battery feed circuit wherein a single transformer is used to perform the functions of battery feed and audio coupling. AC feedback is used to control the dynamic output impedance of the circuit. To achieve a constant dynamic output impedance, the amount of AC feedback is controlled by the DC output voltage, which in turn depends on the loop resistance. To achieve a constant audio gain from the switching network to the subscriber set, the audio signal from the switching network is multiplied by a signal representing the DC output voltage.

Telephone line circuit

A method and means for coding and decoding video signals by repetitive video signal polarity reversal includes the steps of comparing the brightness level of a predetermined time period of the video signal with the brightness level of the video signal over the previous predetermined time period. The polarity of the video signal is inverted or reversed if the difference in brightness level between successive predetermined time periods exceeds a given value.

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Crystal Lake, IL, United States of America

Howard F Jirka