Balancing impedance circuit
AssigneeBell Telephone Laboratories, Incorporated
InventorHarold Seidel
Life of this patent
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Abstract
A class of electronic hybrids is disclosed in which the line balancing impedance is made frequency-sensitive in order to better match the frequency characteristic of the connected line and is made voltage-controlled in order that a single network can be used to match a variety of different gauges of telephone cable pairs. The matching impedances are synthesized utilizing RC networks and the voltage control is realized with two-node Miller effect impedance multiplication circuits realized by long-tailed pairs for synthesizing hyperbolic tangent impedance functions under the control of a voltage.
Claims9
A hybrid balancing impedance for a telephone cable pair characterized by
- a low frequency noninductive resistive-capacitive networkk effective to provide an impedance function inversely proportional to the square root of frequency at low frequencies, and
- a high frequency nonreactive resistive network effective to provide a constant impedance function at high frequencies.
An impedance synthesis circuit comprising
- a first and a second impedance connected in series and each providing a different frequency characteristic in a different frequency range,
- a first multiplier connected to one end of said first impedance,
- a second multiplier connected to the midpoint of said first and second impedances,
- means for summing the outputs of said first and second multipliers and applying the sum to the remaining end of said second impedance, and
- linearly related multiplier control signals connected to said multipliers.
Dependencies are inferred from the claim text.