Differential line bridge for scaleable near-end speech cancellation for tip and ring tone signal detectors

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 voltage 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;
• a switch controller;
• wherein said impedance elements of said sensing elements are chosen such that the difference between said first and second voltage outputs results in attenuated near end speech, said first impedance elements each comprising a first plurality of impedance elements wherein the impedance of each of said first plurality is parallelly coupled into the circuitry by said switch controller such that said first plurality of elements are combined to form the impedance of said first impedance element;
• a third impedance element that is approximately equal to a multiple of said sensing element;
• and
• said second impedance elements each including a second plurality of impedance elements wherein the impedance of each of said second plurality is parallely and selectively coupled into the circuitry by said switch controller such that the sum of the impedance of said third impedance element and the impedance of said second plurality is approximately equal to the impedance of said second impedance element.

Circuitry for near end speech cancellation, said circuitry being coupled to a primary tip and ring lead that is interconnecting a telephone line and a secondary tip and ring lead that is interconnecting subsequent communications equipment, said circuitry comprising:

• a differential line bridge coupled to the tip and ring leads, said differential line bridge 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 connected to one of the primary and 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 second trip 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;
• a differential amplifier having a pair of inputs and coupled to said line bridge such that near end speech energy from the subsequent communications equipment is cancelled;
• first and second voltage 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 and wherein said impedance elements and said sensing elements are chosen such that the difference between said first and second voltage outputs results in attenuated near end speech energy, and
• wherein each said first impedance element impedance is approximately equal to half the scaled value of the impedance of the telephone line impedance and each 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.

Circuitry for near end speech energy cancellation, said circuitry being coupled to a primary tip and ring lead that is interconnecting a telephone line interface and a secondary tip and ring lead that is interconnecting subsequent communications equipment, said circuitry comprising:

• a differential line bridge coupled to the tip and ring leads, said differential line bridge comprising
• a pair of sensing elements, each of said pair of sensing elements being positioned in series with each of the tip and ring leads and wherein each of said pair of sensing elements and the telephone line impedance are connected to form a primary leg of each of an upper and lower bridge;
• and
• first and second voltage outputs, wherein said first voltage output is tapped at a point between one of said pair of first and second impedance elements and said second voltage output is tapped at a point between the other of said pair of first and second impedance elements and wherein said first impedance element impedance is approximately equal to a scaled value of the impedance of the telephone line impedance and said second impedance element is approximately equal to the combined impedance of said scaled value of said sensing element and said first impedance element, whereby said impedance elements and said sensing elements are chosen such that the difference between said first and second voltage outputs results in highly attenuated near end speech energy;
• and
• a differential amplifier having a pair of inputs and coupled to said line bridge.

Circuitry for near end speech cancellation for a tone signal detector, said circuitry comprising:

• a pair of sensing elements, a first of said sensing elements being connected in series between the tip lines connected to a telephone line interface and to a subsequent communications equipment interface and a second of said sensing elements being connected in series between the ring lines of the telephone line interface and the subsequent communications equipment interface,
• a first pair of first impedance elements connected in a first path between the tip line of the telephone line interface and the ring line of the subsequent communications equipment interface,
• a second pair of second impedance elements connected in a second path between the ring line of the telephone line interface and the tip line of the subsequent communications equipment interface,
• each of said first impedance elements comprising a first plurality of individual impedance elements connected in parallel and each of said second impedance elements comprising a second plurality of individual impedance elements connected in parallel and a third impedance element that has an impedance approximately equal to a multiple of the impedance of the sensing elements, said third impedance element being connected in series with said parallel second plurality of second impedance elements, and
• switch means for selectively connecting one of said first and one of said second plurality of individual impedance elements in said first and said second paths.