Patent ID: 6275582
Filing Date: 2001-08-14
Classification: H04M

Abstract:
Circuitry for near end speech cancellation, said circuitry being coupled to primary tip and ring leads that are connected to a telephone line interface and secondary tip and ring leads that are connected to subsequent communications equipment, said circuitry comprising:a pair of sensing elements, one of said sensing elements being positioned in series with the tip leads and the other of said sensing elements being positioned in series with the ring leads;a first and a second pair of series connected first and second impedance elements, the first impedance element of the first pair being series connected to one of the primary tip and ring leads and to one side of a first sensing element, the second impedance element of the first pair being connected to the other of the secondary tip and ring leads and to one side of a second sensing element, the second impedance element of the second pair being connected to the other side of the first sensing element, and the first impedance element of the second pair being connected to the other side of the second sensing element;first and second outputs, said first voltage output being tapped from a point between the first and second impedance elements of the first pair and said second voltage output being tapped from a point between the first and second impedance elements of the second pair; andwherein each of said first impedance element impedance is approximately equal to half the scaled value of the impedance of the telephone line and each of said second impedance element impedance is approximately equal to the combined impedance of said scaled value of said sensing element and said first impedance element, whereby the difference between said first and second voltage outputs results in attenuated near end speech.