Signaling circuit with audible noise reduction

Claim 2

A DX signaling circuit connected between a signal source and a two-wire transmission path comprising a pair of conductors each connected to a different one wire of said path, a signaldetecting circuit including a first relay coil having first and second terminals, said first terminal being coupled to said signal source, a second relay coil having third and fourth terminals, said third terminal being coupled to a source of potential, and means connected between said second terminal and one of said pair of conductors and between said fourth terminal and the other of said pair of conductors responsive to a signal from the second terminal of said first relay coil for applying an equal signal in the same direction to each of said conductors.

Claim 3

A DX signaling circuit connected between a signal source and a two-wire transmission path according to claim 1 wherein said equal signal-applying means comprises a first inductor connected in series between said one conductor and said first relay coil second terminal and a second inductor connected in series between said other conductor and said second relay coil fourth terminal, said inductors being mutually coupled to produce an equal signal in The same direction on each of said conductors.

Claim 4

A DX signaling circuit connected between a signal source and a two-wire line according to claim 2 wherein said detecting circuit further comprises third and fourth relay coils each having two terminals, one terminal of said third relay coil being coupled to said signal source, one terminal of said fourth relay coil being coupled to said potential source, an impedance balancing circuit having two terminals and a further pair of mutually coupled inductors, one of said further pair of mutually coupled inductors being connected between the other terminal of said third relay coil and one terminal of said impedance balancing circuit, the other of said pair of mutually coupled inductors being connected between the other terminal of said fourth relay coil, and the other terminal of said impedance-balancing network, said further pair of mutually coupled inductors being operative to balance the impedances of said first and second inductors.

Claim 5

A DX signaling circuit connected between a signal source and a two-wire trunk associated with a coin telephone line comprising a pair of conductors each connected to a different one wire of said trunk, first relay coil means having first and second terminals, second relay coil means having third and fourth terminals, said first terminal being coupled to said signal source, said third terminal being coupled to a source of potential, said first relay coil means being effective to couple a pulse signal from said signal source to said second terminal, a first inductor connected between said second terminal and one of said conductors, a second inductor connected between said fourth terminal and the other of said conductors, said first and second inductors being mutually coupled and responsive to said pulse signal from said second terminal to produce an equal pulse signal in the same direction on each of said conductors whereby the pulse signal applied to said line is simplexed.

Claim 6

A DX signaling circuit connected between a signal source and a two-wire trunk associated with a coin telephone line comprising a pair of conductors each connected to a different one wire of said trunk, first relay coil means having first and second terminals, second relay coil means having third and fourth terminals, said first terminal being coupled to said signal source, said third terminal being coupled to a source of potential, said first relay coil means being effective to couple a pulse signal from said signal source to said second terminal, a first inductor connected between said second terminal and one of said conductors, a second inductor connected between said fourth terminal and the other of said conductors, said first and second inductors being mutually coupled and responsive to said pulse signal from said second terminal to produce an equal pulse signal in the same direction on each of said conductors whereby the pulse signal applied to said line is simplexed.

Claim 7

A DX signaling circuit according to claim 4 wherein said first and second inductors are mutually coupled inductors operative to couple the audible-frequency portion of said pulse from said second terminal to the other conductor.

Claim 8

In a telephone system having a two-wire line connected between a local office and a toll office, a signaling circuit comprising a signal source, first and second conductors, said first conductor being connected to one wire of said line and said second conductor being connected to the other wire of said line, first relay coil means having a first terminal coupled to said signal source and a second terminal, said first relay coil means being effective to couple a signal from said signal source to said second terminal, second relay coil means having a third terminal coupled to a source of potential and a fourth terminal, means connected between said second terminal and said first conductor and between said fourth terminal and said second conductor for coupling the audible frequency portion of said signal from said second terminal to said first conductor and to said second conductor, said signal-coupling means being operative to produce an equal audible-frequency signal in the same direction on each of said first and second conductors.

Claim 9

In a telephone system having a two-wire line connected between a local office and a toll office, a signaling circuit comprising a signal source, first and second conductors, said first conductor being connected to one wire of said line and said second conductor being connected to the other wire of said line, first relay coil means having a first terminal coupled to said signal source and a second terminal, said first relay coil means being effective to couple a signal from said signal source to said second terminal, second relay coil means having a third terminal coupled to a source of potential and a fourth terminal, means connected between said second terminal and said first conductor and between said fourth terminal and said second conductor for coupling the audible frequency portion of said signal from said second terminal to said first conductor and to said second conductor, said signal-coupling means being operative to produce an equal audible-frequency signal in the same direction on each of said first and second conductors.

Claim 10

In a telephone system having a two-wire connected between a local office and a toll office, a signaling circuit according to claim 6 wherein said signal-coupling means comprises a pair of inductors, one inductor being connected between said second terminal and said first conductor and the other inductor being connected between said fourth terminal and said second conductor, said inductors being magnetically coupled to produce an audible-frequency signal on said second conductor equal in magnitude and in the same direction as the audible-frequency portion of the signal applied to said first conductor from said second terminal.