Subscriber loop extension unit

Claim 2

In a two wire transmission system having at least one dial pulse signalling path and an alternating current path in parallel circuit relationship with the signalling path, a direct current isolating circuit in the signalling path comprising: means for generating a periodically varying signal; means for controlling the operation of the signal generating means responsive to dial pulse signals in the system; and periodically varying signal coupling means for transmitting an output from the signal generating means into the signalling path and for providing direct current signal isolation along the signalling path.

Claim 3

A circuit according to claim 1 wherein the means for generating a periodically varying signal is a free running multivibrator.

Claim 4

A circuit acCording to claim 2 wherein the periodically varying signal coupling means is a transformer having a primary winding connected to the output of the multivibrator.

Claim 5

A circuit according to claim 3 including a central office pulsing transistor connected to a secondary winding of the transformer.

Claim 6

A circuit according to claim 4 wherein the controlling means is a sensing circuit for detecting the presence of direct current in the transmission system.

Claim 7

A unit for extending the range of a two wire transmission circuit having a tip side and a ring side comprising: an alternating signal transmission circuit interconnecting a central switching location and station equipment located remotely with respect to the switching location; a ringing signal path connected in parallel circuit relationship with the transmission circuit; switch means connected to the alternating signal transmission circuit and said first signal path; a source of ringing signals connected to the switching means; circuit means connected to the source of signals and the switching means for controlling the operation of said switching means and disconnecting the signal source from the station equipment, said circuit means being responsive to an off-hook condition at the station equipment; a direct current isolating signal path including a dial pulse repeater for transmitting pulsing signals from the station equipment to the central switching location connected in parallel circuit relationship with the transmission circuit and the ringing signal path and a source of electrical power connected to said direct current signal path and the switching means.

Claim 8

A unit for extending the range of a two wire transmission circuit having a tip side and a ring side comprising: an alternating signal transmission circuit interconnecting a central switching location and station equipment located remotely with respect to the switching location; a ringing signal path connected in parallel circuit relationship with the transmission circuit; switch means connected to the alternating signal transmission circuit and said first signal path; a source of ringing signals connected to the switching means; circuit means connected to the source of signals and the switching means for controlling the operation of said switching means and disconnecting the signal source from the station equipment, said circuit means being responsive to an off-hook condition at the station equipment; a direct current isolating signal path including a dial pulse repeater for transmitting pulsing signals from the station equipment to the central switching location connected in parallel circuit relationship with the transmission circuit and the ringing signal path and a source of electrical power connected to said direct current signal path and the switching means.

Claim 9

A unit according to claim 6 wherein the transmission circuit includes a balanced transformer having a primary winding connected to the central office tip and ring side of the circuit and a secondary winding connected to the subscriber tip and ring side of the circuit.

Claim 10

A unit according to claim 7 wherein the first signal path includes a detector circuit for sensing the presence of ringing signals transmitted from the central switching location.

Claim 11

A unit according to claim 8 wherein the switching means is a relay operable responsive to the detector circuit for selectively connecting the alternating signal transmission circuit or the source of signals to the station equipment.

Claim 12

A unit according to claim 9 wherein the source of signals is a ringing signal generator located in the central switching location.

Claim 13

A unit according to claim 9 wherein the source of signals is a local ringing signal generator associated with the unit.

Claim 14

A unit according to claim 9 wherein the circuit means is a ring trip relay operable responsive to connection of the station equipment to the transmission circuit.

Claim 15

A unit according to claim 12 wherein the second signal path includes a dial pulse repeater circuit for transmitting dial signaling pulses from the station equipment to the central switching location.

Claim 16

A unit according to claim 13 wherein the dial pulse repeater circuit includes a free running multivibrator and a transformer for providing DC isolation of the unit from the central office.

Claim 17

A unit according to claim 14 including an auxiliary power source connectible to the unit.

Claim 18

A unit for extending the range of an exchange telephone circuit comprising: a voice frequency transmission circuit interconnecting a telephone central office and station equipment at a subscriber location; a dial pulse repeater connected in parallel circuit relationship with the voice frequency transmission circuit; said dial pulse repeater comprising a subscriber switching circuit, a signal generator connected to the output of the subscriber switching circuit and a central office switching circuit connected to the output of the signal generator; first switching means connected in the transmission circuit for controlling the transmission of ringing signals to said station equipment and for controllinG the interruption of said voice frequency transmission circuit; and second switching means connected to the first switching means for controlling said first switching means, said second switching means being responsive to connection of the station equipment to the telephone circuit to disconnect the ringing signals from the station equipment and to control the completion of continuity of the voice frequency transmission circuit.

Claim 19

A unit for extending the range of an exchange telephone circuit comprising: a voice frequency transmission circuit interconnecting a telephone central office and station equipment at a subscriber location; a dial pulse repeater connected in parallel circuit relationship with the voice frequency transmission circuit; said dial pulse repeater comprising a subscriber switching circuit, a signal generator connected to the output of the subscriber switching circuit and a central office switching circuit connected to the output of the signal generator; first switching means connected in the transmission circuit for controlling the transmission of ringing signals to said station equipment and for controllinG the interruption of said voice frequency transmission circuit; and second switching means connected to the first switching means for controlling said first switching means, said second switching means being responsive to connection of the station equipment to the telephone circuit to disconnect the ringing signals from the station equipment and to control the completion of continuity of the voice frequency transmission circuit.

Claim 20

A unit according to claim 16 wherein the central office switching circuit includes a transformer connected to the output of the signal generator for providing DC isolation of the dial pulse repeater from the central office.

Claim 21

A unit according to claim 16 including a ringing signal detector connected in parallel circuit relationship with the voice frequency transmission circuit and the dial pulse repeater.

Claim 22

A unit according to claim 18 wherein the first switching means is a ring relay operable responsive to the ringing signal detector for selectively connecting the voice frequency transmission circuit or a source of ringing signals to the station equipment.

Claim 23

A unit according to claim 19 wherein the second switching means is a ring trip relay operable responsive to an off-hook signal from the station equipment for controlling the connection of ringing signals to the station equipment through the ring relay.

Claim 24

A unit according to claim 20 including an auxiliary power source connected to the subscriber switching circuit and the signal generator operable responsive to operations of the signal generation for supplying current to that portion of the circuit between the unit and the station equipment.