Patent ID: 6628779
Filing Date: 2003-09-30
Classification: H04B

Abstract:
A combination for near end speech cancellation connected to the tip and ring interface leads of a loop to which is attached office equipment, said combination comprising:a first impedance element in series with one of the tip and ring interface leads, said first impedance element and an impedance of the loop and office equipment connected to the tip and ring leads forming one half of a Wheatstone bridge having a center; network means and a scalable impedance element connected in series with said network means and forming the other half of the Wheatstone bridge, an impedance of the network means matching the impedance of the loop and office equipment connected to the tip and ring leads multiplied by a factor of K and the scalable impedance matching the impedance of the first impedance element, also multiplied by the factor of K where K is greater than 1; a detector connected across the center of the Wheatstone bridge, said detector being connected to the connection point between the first impedance element and the impedance of the loop and office equipment in said one half of the Wheatstone bridge and the connection point between said network means and the scalable impedance element of said other half of the Wheatstone bridge; and a system controller for altering the impedance of said scalable impedance element to cause said scalable impedance element to mirror the impedance of said first impedance element by the factor of K.