On premise telephone loop tester

Abstract

The instant invention relates to a device that permits a telephone line (loop) to be tested from a telephone central office, thereby eliminating the expense resulting from a visit by a repairman to a subscriber's premises. The disclosed device is responsive to an audio tone of a predetermined frequency, is located on a subscriber's premises and is activated by an audio tone of frequency within the pass band of the telephone circuit, this tone being transmitted from a central office. A tuned detector, located within the device, upon receiving said predetermined tone, actuates a timing circuit and relay circuit that places a circuit across the tip and ring of a telephone line. The circuit simulates the electrical condition of a telephone instrument in the "off hook" position and causes central office line equipment to operate, if the telephone loop is in an operable state, thereby indicating that the telephone loop is complete from the central office to the subscriber's premises.

I claim: 
     
       1. A telephone loop tester comprising first and second conductors adapted to be electrically connected by a talking pair of conductors of a telephone transmisson line to a central office in a telephone transmission system that has a telephone set connected to said central office by said transmission line, and circuit means connected to said first and second conductors and responsive to the application of a predetermined, central office-transmitted signal to said first and second conductors for electrically simulating an off hook condition of said telephone set without disconnecting said telephone set from said central office by completing a current conducting path between said talking pair of conductors at a location that is remote from said central office.[...]..Iadd., said predetermined signal having a pre-selected frequency, and means for rendering said circuit means non-responsive to signals having said pre-selected frequency in response to the transfer of said telephone set to its off hook state. .Iaddend. .[.2. The telephone loop tester defined in claim 1 wherein said predetermined signal has a pre-selected frequency and wherein means are provided for rendering said circuit means non-responsive to signals having said pre-selected frequency in response to the transfer of said telephone set to its off hook 
     
     
        state..].  3. A telephone loop tester comprising .Iadd.tuned .Iaddend.detecting means adapted to be connected to a central office by a talking pair of conductors of a telephone transmission line in a telephone system that has a telephone set connected to said central office by said transmission line, said detecting means being operative to detect a signal of pre-selected frequency that is transmitted by said talking pair of conductors from said central office .[.and.]. means responsive to the detection of said signal of pre-selected frequency by said detecting means for electrically simulating an off hook condition of said telephone set remotely from said central office to provide an off hook signal while said telephone set is in its on hook state and without disconnecting said telephone set from said central office.[...]..Iadd., said means for simulating said off hook condition of said telephone set comprising a circuit rendered effective by said detecting means upon detecting said signal of pre-selected frequency for completing a current-conducting circuit path that bridges said conductors in parallel relation with said telephone set and means rendered effective by the completion of said current-conducting circuit path for preventing application of a detectable signal to said detecting means while said current-conducting circuit path is completed. .Iaddend. .[.4. The telephone loop tester defined in claim 3 wherein said means for simulating said off hook condition of said telephone set comprises a circuit rendered effective by said detecting means upon detecting said signal of pre-selected frequency for completing a current-conducting circuit path that bridges said conductors in parallel relation with said telephone set..].  .[.5. The telephone loop tester defined in claim 4 comprising means rendered effective by the completion of said current-conducting circuit path for preventing application of a detectable signal to said detecting means while said current-conducting circuit path is completed..].  .[.6. The telephone loop tester defined in claim 4 comprising a unidirectional current-conducting device connected to said detecting means for blocking application of detectable signals to said detecting means whenever said telephone set is in its off hook 
     
     
        state..].  7. The telephone loop tester defined in claim .[.6.]. .Iadd.31 .Iaddend.wherein said unidirectional current-conducting device and said detecting means are connected in series, and wherein said means for completing said current-conducting circuit path comprises switch means in 
     
     
        parallel with said detecting means and said device. 8. The telephone loop tester defined in claim .[.4.]. .Iadd.3 .Iaddend.wherein said circuit rendered effective by said detecting means comprises means for disabling said .[.circuit.]. .Iadd.current .Iaddend.path after a pre-selected time delay. .[.9. In a telephone transmission system having a subscriber's telephone set and a talking pair of conductors connecting said telephone set to a central office, the improvement comprising means connected to said conductors remotely from said central office and responsive to a central office-transmitted signal of pre-selected frequency for electrically simulating an off hook condition of said telephone set by causing an off hook signal to be sent back to said central office as if said telephone set were actually transferred to its off hook state and without disconnecting said telephone set from said central office..]. .[.10. In a telephone transmission system, a subscriber's telephone instrument, a two conductor transmission line connecting said telephone instrument to a central office, and a telephone loop testing circuit electrically connected to the conductors of said transmission line remotely from said central office and comprising means for detecting a central office-transmitted signal of pre-selected frequency when said telephone instrument is in its on hook state, and means responsive to the detection of said signal of pre-selected frequency by said detecting means for completing a circuit between said conductors in parallel with said telephone instrument while said telephone instrument is in its on hook state and without disconnecting said telephone instrument from said central office to provide an off hook signal as if said telephone instrument were actually transferred to its off hook state..].  .[.11. A telephone loop tester for a telephone transmission system that has a subscriber's telephone instrument connected by a two-conductor transmission line to central office equipment at a central office, said telephone loop tester comprising first and second conductors adapted to be connected to the conductors of said transmission line remotely from said central office and circuit means connected to aid first and second conductors and responsive to a pre-selected central office-transmitted signal for simulating an off hook condition of said telephone instrument to provide an off hook signal that is capable of operating said central office equipment as if said telephone instrument were actually transferred to its off hook state without disconnecting said telephone instrument from said central office and while said telephone instrument is in its on hook state, the failure of said central office equipment to operate upon transmittal of said pre-selected signal providing an indication that a fault or trouble may exist in said line..].  .[.12. In a telephone transmission system having a subscriber's telephone instrument and a talking pair of conductors connecting said telephone instrument to central office line equipment at a central office, the improvement comprising a circuit connected to said conductors remotely from said central office and responsive to a central office-transmitted signal of pre-selected frequency for simulating an off hook condition of said telephone instrument to provide an off hook signal that is capable of operating said central office equipment as if said telephone instrument were actually transferred to its off hook state without disconnecting said telephone instrument from said central office and while said telephone instrument is 
     
     
        in its on hook state..].  13. In a telephone transmission system, a subscriber's telephone instrument and a talking pair of conductors for connecting said telephone instrument to a central office, said conductors being adapted to be connected to central office-located equipment that is capable of being operated by the off hook signal that is produced by transference of said telephone instrument to its off hook state, and a telephone loop tester connected to said conductors remotely from said central office and comprising means for detecting a central office-transmitted signal of pre-selected frequency and a circuit responsive to the detection of said central office-transmitted signal by said detecting means for completing a current-conducting circuit path that bridges said conductors in parallel with said telephone instrument to provide an off hook signal that is capable of operating said equipment as if said telephone instrument were actually transferred to its off hook state without disconnecting said telephone instrument from said central office and while said telephone instrument is in its on hook state.[...]..Iadd., said telephone loop tester further comprising means in series circuit relationship with said detecting means and rendered effective by the transfer of said telephone instrument to its off hook state to block application of detectable signals to said detecting means and thereby prevent the detection of a central office-transmitted signal of said pre-selected frequency whenever said telephone instrument is in its off hook state. .Iaddend. .[.14. The telephone transmission system defined in claim 13 wherein said telephone loop tester further comprises means in series circuit relationship with said detecting means and rendered effective by the transfer of said telephone instrument to its off hook state to block application of detectable signals to said detecting means and thereby prevent the detection of a central office-transmitted signal of said pre-selected frequency whenever said telephone instrument 
     
     
        is in its off hook state..].  15. In a telephone transmission system, a telephone instrument and a talking pair of conductors for connecting said telephone instrument to a central office, said conductors being adapted to be connected to central office-located equipment that is capable of being operated by transference of said telephone instrument to its off hook state, and a telephone loop testing circuit connected to said conductors remotely from said central office and comprising means for detecting a central office-transmitted signal of pre-selected frequency, switch means connected between said conductors in parallel with said telephone instrument, said switch means being capable of being conditioned to complete a current conducting path that bridges said conductors in parallel with said telephone instrument, means rendered effective by said detecting means upon the detection of said central office-transmitted signal for .[.conditioning.]. .Iadd.conducting .Iaddend.said switch means to complete said current conducting path, said current conditioning path being effective upon being completed to cause operation of said equipment as if said telephone instrument were transferred to its off hook state and without disconnecting said telephone instrument from said central office.[...]..Iadd., said switch means being connected in parallel circuit relationship with said detecting means, and said loop testing circuit further comprising a unidirectional current-conducting device in series with said detecting means for blocking the application of detectable signals to said detecting means whenever said telephone instrument is in its off hook state to thereby prevent the detection of a signal of said pre-selected frequency whenever said telephone instrument is in its off hook state. .Iaddend. .[.16. The telephone transmission system defined in claim 15 wherein said switch means is connected in parallel circuit relationship with said detecting means..].  .[.17. The telephone transmission system defined in claim 16 wherein said loop testing circuit comprises a unidirectional current conducting device in series with said detecting means for blocking the application of detectable signals to said detecting means whenever said telephone instrument is in its off hook state to thereby prevent the detection of a signal of said pre-selected frequency whenever said telephone instrument is in its off hook state..]. 
     
     
        .[.18.  The telephone transmission system defined in claim 15 wherein said means for conditioning said switch means to complete said current conducting path includes time delay means rendered effective by the detection of said signal of pre-selected frequency for conditioning said switch means to disable said current conducting path upon expiration of a pre-selected time following the detection of said signal of pre-selected frequency by said detecting means..].  .[.19. The telephone transmission system defined in claim 18 wherein said loop testing circuit further comprises means for blocking application of a detectable signal to said detecting means while said current conducting path is completed..]. .[.20. A telephone loop tester comprising detecting means adapted to be connected to a central office by a talking pair of conductors of a telephone transmission line in a telephone transmission system that has a telephone instrument connected to said central office by said transmission line, said detecting means being effective to detect a central office-transmitted signal of pre-selected frequency, and circuit means responsive to the detection of said signal by said detecting means for completing a current-conducting circuit path that bridges said talking pair of conductors in parallel with said telephone instrument and remotely from said central office to provide an off hook signal as if said telephone instrument were actually transferred to its off hook state without disconnecting said telephone instrument from said central office and while said telephone instrument is in its on hook state..].  .Iadd. 21. A telephone loop tester adapted to be electrically connected to a transmission medium in a telephone system in which said transmission medium provides a two way transmission path between a subscriber's telephone and a central office and includes tip and ring conductors connected to said telephone set, said telephone loop tester comprising a signal detecting circuit for detecting a pre-selected central office-originated signal which is fed to the detector circuit from said transmission medium, means responsive to the detection of said pre-selected signal by said detecting circuit for completing a current shunt across said ring and tip conductors without disconnecting said telephone set from said central office and without transferring said telephone set to its off hook condition, said shunt upon being completed beng effective to cause a change in an electrical condition which is detectable at said central office if said transmission medium is operable, and a unidirectional current-conducting device electrically connected to said detecting circuit for blocking application of detectable signals to said detecting circuit whenever said telephone set is in its off hook state. .Iaddend. .Iadd. 22. A telephone loop tester adapted to be electrically connected to a talking pair of conductors in a telephone system in which the talking pair of conductors is connected to a subscriber's telephone equipment and forms at least a part of a transmission facility that connects said telephone equipment to a central office, said telephone loop tester comprising a tuned detector for sensing a central office-originated test signal of pre-selected frequency which is transmitted by said transmission facility to said tuned detector, means responsive to the sensing of said test signal by said tuned detector for completing a current-conducting path across the conductors of said talking pair without transferring said telephone equipment to its off hook condition, said current-conducting path upon being completed being effective to cause a change in an electrical condition that is detectable at said central office to provide an indication that said transmission facility is operative apart from the subscriber's telephone equipment, and means rendered effective by the completion of said current-conducting path for preventing application of a detectable test signal to said detector while said path is completed. .Iaddend..Iadd. 23. A telephone loop tester adapted to be electrically connected to a talking pair of conductors in a telephone system in which the talking pair of conductors is connected to a subscriber's telephone equipment and forms at least a part of a transmission facility that connects said telephone equipment to a central office, said telephone loop tester comprising a tuned detector for sensing a central office-originated test signal of pre-selected frequency which is transmitted by said transmission facility to said tuned detector, means responsive to the sensing of said test signal by said tuned detector for completing a current-conducting path across the conductors of said talking pair without transferring said telephone equipment to its off hook condition, said current-conducting path upon being completed being effective to cause a change in an electrical condition that is detectable at said central office to provide an indication that said transmission facility is operative apart from the subscriber's telephone equipment, and a unidirectional current-conducting device electrically connected to said detector for blocking application of detectable test signals to said detector whenever said telephone equipment is in its off hook state. .Iaddend. .Iadd. 24. The telephone loop tester defined in claim 23, wherein said unidirectional current-conducting device and said detector are electrically connected in series, and wherein said means for completing said current-conducting path comprises switch means in parallel with said detector and said device. .Iaddend. .Iadd. 25. A telephone loop tester adapted to be electrically connected to a talking pair of conductors in a telephone system in which the talking pair of conductors is connected to a subscriber's telephone equipment and forms at least a part of a transmission facility that connects said telephone equipment to a central office, said telephone loop tester comprising a tuned detector for sensing a central office-originated test signal of pre-selected frequency which is transmitted by said transmission facility to said tuned detector, means responsive to the sensing of said test signal by said tuned detector for completing a current-conducting path across the conductors of said talking pair without transferring said telephone equipment to its off hook condition, said current-conducting path upon being completed being effective to cause a change in an electrical condition that is detectable at said central office to provide an indication that said transmission facility is operative apart from the subscriber's telephone equipment, and means rendered effective by the transfer of said telephone equipment to the off hook state to block application of the test signal to said detector. .Iaddend. .Iadd. 26. A telephone loop tester adapted to be electrically connected to a talking pair of conductors in a telephone system in which the talking pair of conductors is connected to a subscriber's telephone equipment and forms at least a part of a transmission facility that connects said telephone equipment to a central office, said telephone loop tester comprising a tuned detector for sensing a central office-originated test signal of pre-selected frequency which is transmitted by said transmission facility to said tuned detector, means responsive to the sensing of said test signal by said tuned detector for completing a current-conducting path across the conductors of said talking pair without transferring said telephone equipment to its off hook condition, said current-conducting path upon being completed being effective to cause a change in an electrical condition that is detectable at said central office to provide an indication that said transmission facility is operative apart from the subscriber's telephone equipment, and means rendered effective by the transfer of said telephone equipment to the off hook state for preventing the completion of said current-conducting path by the transmission of said test signal as long as said telephone equipment is in the off hook state. .Iaddend. .Iadd. 27. The telephone loop tester defined in claim 26, comprising a time delay circuit responsive to the detection of said test signal by said detector for maintaining said current-conducting path completed for a pre-selected time interval following termination of the detected test signal. .Iaddend. .Iadd. 28. A telephone loop tester adapted to be electrically connected to a talking pair of conductors in a telephone system in which the talking pair of conductors is connected to a subscriber's telephone equipment and forms at least a part of a transmission facility that connects said telephone equipment to a central office, said telephone loop tester comprising a frequency-discriminating, tuned detector for sensing a test signal of pre-selected frequency which is transmitted by way of said facility to said detector, means responsive to the sensing of said test signal by said detector for completing a circuit across the conductors of said talking pair to cause a change in a predetermined electrical condition that is detectable at the central office to provide an indication that said facility is operative apart from said telephone equipment, and means rendered effective by the transfer of said telephone equipment to the off hook state for preventing the completion of said circuit upon the transmittal of said test signal as long as said telephone equipment is in the off hook state. .Iaddend. .Iadd. 29. The telephone loop tester defined in claim 28 wherein said detector is a resonant circuit. .Iaddend..Iadd. 30. The telephone loop tester defined in claim 28 comprising a time delay circuit responsive to the sensing of said test signal by said detector for maintaining said current-conducting path completed for a pre-selected time interval following termination of the sensed test signal. .Iaddend. .Iadd. 31. A telephone loop tester comprising tuned detecting means adapted to be connected to a central office by a talking pair of conductors of a telephone transmission line in a telephone system that has a telephone set connected to said central office by said transmission line, said detecting means being operative to detect a signal of pre-selected frequency that is transmitted by said talking pair of conductors from said central office, means responsive to the detection of said signal of pre-selected frequency by said detecting means for electrically simulating an off hook condition of said telephone set remotely from said central office to provide an off hook signal while said telephone set is in its on hook state and without disconnecting said telephone set from said central office, said means for simulating said off hook condition of said telephone set comprising a circuit rendered effective by said detecting means upon detecting said signal of pre-selected frequency for completing a current-conducting circuit path that bridges said conductors in parallel relation with said telephone set, and a unidirectional current-conducting device connected to said detecting means for blocking application of detectable signals to said detecting means whenever said telephone set is in its off hook state. .Iaddend..Iadd. 32. In a telephone transmission system, a telephone instrument and a talking pair of conductors for connecting said telephone instrument to a central office, said conductors being adapted to be connected to central office-located equipment that is capable of being operated by transference of said telephone instrument to its off hook state, and a telephone loop testing circuit connected to said conductors remotely from said central office and comprising means for detecting a central office-transmitted signal of pre-selected frequency, switch means connected between said conductors in parallel with said telephone instrument, said switch means being capable of being conditioned to complete a current conducting path that bridges said conductors in parallel with said telephone instrument, means rendered effective by said detecting means upon the detection of said central office-transmitted signal for conditioning said switch means to complete said current conducting path, said current conducting path being effective upon being completed to cause operation of said equipment as if said telephone instrument were transferred to its off hook state and without disconnecting said telephone instrument from said central office, said means for conditioning said switch means to complete said current conducting path including time delay means rendered effective by the detection of said signal of pre-selected frequency for conditioning said switch means to disable said current-conducting path upon expiration of a pre-selected time following the detection of said signal of pre-selected frequency by said detecting means, and said loop testing circuit further comprising means for blocking application of a detectable signal to said detecting means while said current-conducting path is completed. .Iaddend.