Telephone subscriber line system intra call apparatus and method

Claim 2

In a telephone subscriber concentrator system having a remote unit connecting a group of subscriber lines to a set of trunks connected to a central office unit, the central office unit providing a group of lines from said set of trunks corresponding to said group of subscriber lines, the central office unit including a memory unit containing information as to the connection of lines and trunks at said remote unit and central office unit, improved apparatus in said central office unit for detecting an intra call between a calling line and a called line at said remote unit wherein a trunk associated with the calling line at the remote unit is initially linked at the central office with a trunk associated with the called line at the remote unit comprising a. generator bus means selectively connectable to any one of said trunks, b. a plurality of first switch means connEcted respectively to each trunk and responsive to a control signal for selectively connecting said generator bus means to a respective trunk, c. a plurality of latch circuit means connected respectively to each trunk for applying a control signal to said first switch means to connect the respective trunk to said generator bus means when said trunk is the called trunk connected to a called line that is off hook in response to ringing, d. generator means for applying a detectable signal to said generator bus means when the latch circuit means connected to a trunk is applying a control signal, e. detector bus means connectable to any one of said trunks, f. a plurality of second switch means connected respectively to each trunk for selectively connecting said detector bus means to a respective trunk, and g. means connected to said detector bus means for detecting said detectable signal on said detector bus means when said detector bus means is connected to the calling trunk which is linked to said called trunk on which said detectable signal is applied.

Claim 3

The combination of claim 1 wherein said latch circuit means applies said control signal to the one of said first switch means connected to the called trunk in response to a pulse signal when said called trunk is connected to a line that is off hook in response to ringing, and the one of said second switch means connected to the calling trunk connects said detector bus means to a trunk in response to a pulse signal, and further comprising pulse scanning means for sequentially applying a pulse signal to each of said latch circuit means and each of said second switch means.

Claim 4

The combination of claim 2 wherein said generator means comprises means connected to said generator bus means for sensing a connection between said generator bus means and a trunk and for providing a signal generator control signal in response thereto, and signal generator means for applying a detectable signal to said generator bus means in response to said signal generator control signal.

Claim 5

The combination of claim 2 wherein said signal detecting means comprises means connected to said detector bus means for comparing said signal received on said detector bus means to said signal applied to said generator bus means to generate a verification signal when said signals are close to each other in frequency.

Claim 6

The combination of claim 4 wherein said pulse scanning means comprises a plurality of lines connected respectively to each of said latch circuit means and each of said second switch means connected to each trunk, means for generating a train of pulses at a first repetition rate and at a second repetition rate slower than said first rate, said pulses applied sequentially to said plurality of lines, means for controlling the repetition rate of said pulse train generating means to provide pulses at said first rate until said sensing means senses a connection between said generator bus means and a trunk and to provide pulses at said second rate until said verification signal is generated.

Claim 7

The combination of claim 4 wherein said signal comparing means comprises band pass filter means connected to said detector bus means, threshold detector means connected to the output of said band pass filter means, and frequency comparing means receiving the signal from said threshold detector means and the signal applied to said generator bus to provide a verification signal when said signals are close to each other in frequency.

Claim 8

The combination of claim 6 wherein said signal generated by said signal generator means is a square wave signal and said threshold detector means provides a square wave output, and said frequency comparing means comparing said square wave signals comprises digital logic means.

Claim 9

The combination of claim 2 wherein said digital logic means comprises a first n-bit shift register having the square wave signal from said threshold detectOr means applied to the shift input thereof, a second n-bit shift register having the square wave signal from said signal generator means applied to the shift input thereof, a first inverter connected between the nth bit output and the input of said first register, a second inverter connected between the nth bit output and the input of said second register, n exclusive-OR gates each receiving the corresponding output lines of the first and second registers, and an AND gate receiving the outputs of said exclusive-OR gates.

Claim 10

In a telephone subscriber concentrator system having a remote unit connecting a group of subscriber lines to either a set of trunks connected to a central office unit or to an intra-link in the remote unit, the central office unit providing a group of lines from said set of trunks corresponding to said group of subscriber lines, the central office unit including a memory unit containing information as to the connection of lines and trunks at said remote unit and said central office unit, said central office having a data link to said remote unit, improved apparatus in said central office unit for detecting an intra-call and establishing an intra-link at said remote unit wherein a connection is initially made between a calling line and a called line at the remote unit via a first trunk connected between the remote unit and the central office, said first trunk connected to the calling line and designated the calling trunk, a link at the central office, and a second trunk connected between the remote unit and the central office connected to the called line and designated the called trunk comprising a. means including means for high speed DC scanning of said set of trunks for detecting the initial connection of a trunk to a called line, whereby said trunk is the called trunk, b. means for applying a detectable signal to said called trunk, thereby applying said detectable signal to the calling trunk which is connected to said called trunk at the central office, c. means for searching at a slow speed relative to said high speed DC scanning the remaining trunks in said set of trunks to detect said signal on said calling trunk to thereby identify said calling trunk, d. means responsive to said detected signal and said memory unit for instructing said remote unit via said data link to connect said calling line corresponding to said calling trunk to said intra-link, e. means including said means for high speed DC scanning of said set of trunks for identifying said called trunk and for instructing said remote unit via said data link to connect said called line corresponding to said called trunk to said intra-link, and f. means for releasing said called and calling trunks.

Claim 11

In a telephone subscriber concentrator system having a remote unit connecting a group of subscriber lines to either a set of trunks connected to a central office unit or to an intra-link in the remote unit, the central office unit providing a group of lines from said set of trunks corresponding to said group of subscriber lines, the central office unit including a memory unit containing information as to the connection of lines and trunks at said remote unit and said central office unit, said central office having a data link to said remote unit, improved apparatus in said central office unit for detecting an intra-call and establishing an intra-link at said remote unit wherein a connection is initially made between a calling line and a called line at the remote unit via a first trunk connected between the remote unit and the central office, said first trunk connected to the calling line and designated the calling trunk, a link at the central office, and a second trunk connected between the remote unit and the central office connected to the called line and designated the called trunk comprising a. means including means for high speed DC scanning of said set of trunks for detecting the initial connection of a trunk to a called line, whereby said trunk is the called trunk, b. means for applying a detectable signal to said called trunk, thereby applying said detectable signal to the calling trunk which is connected to said called trunk at the central office, c. means for searching at a slow speed relative to said high speed DC scanning the remaining trunks in said set of trunks to detect said signal on said calling trunk to thereby identify said calling trunk, d. means responsive to said detected signal and said memory unit for instructing said remote unit via said data link to connect said calling line corresponding to said calling trunk to said intra-link, e. means including said means for high speed DC scanning of said set of trunks for identifying said called trunk and for instructing said remote unit via said data link to connect said called line corresponding to said called trunk to said intra-link, and f. means for releasing said called and calling trunks.

Claim 12

The combination of claim 4 wherein said called line is a line that is off hook in response to ringing, and said means for detecting the initial connection of a trunk to a called line comprises a latch circuit means for providing a control signal when said trunk is connected to a line that is off hook in response to ringing.

Claim 13

The combination of claim 10 wherein said means for applying a detectable signal to a trunk comprises a. generator bus means selectively connectable to any one of said trunks, b. switch means responsive to said control signal for connecting said trunk to said generator bus means, and c. means for applying said detectable signal to said generator bus means.

Claim 14

The combination of claim 9 wherein said means for searching the remaining trunks comprises a. detector bus means selectively connectable to any one of said trunks, b. means for sequentially connecting each of said remaining trunks to said generator bus means, and c. detector means connected to said detector bus means for detecting said signal.

Claim 15

The combination of claim 12 wherein said means for applying a detectable signal includes signal generator means and wherein said detector means is connected to Said generator means for comparing said signal detected on said detector bus means to said detectable signal applied to said generator bus means to generate a verification signal when said signals are within a predetermined frequency tolerance.

Claim 16

The combination of claim 11 wherein said means for identifying said called trunk comprises a. means for sequentially applying a disconnect signal to each of said means for connecting said trunk to said generator bus means, and b. means for monitoring the current flow in said generator bus means for detecting a current change when the called trunk is disconnected from said generator bus means whereby the called trunk is identified.

Claim 17

The combination of claim 8 wherein said trunks are scanned about 8 thousand times per second.

Claim 18

In a telephone subscriber concentrator system having a remote unit connecting a group of subscriber lines to either a set of trunks connected to a central office unit or to an intra-link in the remote unit, the central office unit providing a group of lines from said set of trunks corresponding to said group of subscriber lines, the central office unit including a memory unit containing information as to the connection of lines and trunks at said remote unit and said central office unit, said central office unit having a data link to said remote unit, the improved method in said central office unit for detecting an intra-call and establishing an intra-link at said remote unit wherein a connection is initially made between a calling line and a called line at the remote unit via a first trunk connected between the remote unit and the central office, said first trunk connected to the calling line and designated the calling trunk, a link at the central office, and a second trunk connected between the remote unit and the central office connected to the called line and designated the called trunk comprising high speed DC scanning said set of trunks to detect the initial connection of a trunk to a called line, whereby said trunk is the called trunk, applying a detectable signal to said called trunk, thereby applying said detectable signal to the calling trunk which is connected to said called trunk at the central office, searching at a slow speed relative to said high speed DC scanning the remaining trunks in said set of trunks to detect said signal on said calling trunk to thereby identify the calling trunk, instructing said remote unit via said data link to connect said calling line corresponding to said calling trunk to said intra-link, identifying said called trunk and for instructing said remote unit via said data link to connect said called line corresponding to said called trunk to said intra-link, and releasing said called and calling trunks.

Claim 19

In a telephone subscriber concentrator system having a remote unit connecting a group of subscriber lines to either a set of trunks connected to a central office unit or to an intra-link in the remote unit, the central office unit providing a group of lines from said set of trunks corresponding to said group of subscriber lines, the central office unit including a memory unit containing information as to the connection of lines and trunks at said remote unit and said central office unit, said central office unit having a data link to said remote unit, the improved method in said central office unit for detecting an intra-call and establishing an intra-link at said remote unit wherein a connection is initially made between a calling line and a called line at the remote unit via a first trunk connected between the remote unit and the central office, said first trunk connected to the calling line and designated the calling trunk, a link at the central office, and a second trunk connected between the remote unit and the central office connected to the called line and designated the called trunk comprising high speed DC scanning said set of trunks to detect the initial connection of a trunk to a called line, whereby said trunk is the called trunk, applying a detectable signal to said called trunk, thereby applying said detectable signal to the calling trunk which is connected to said called trunk at the central office, searching at a slow speed relative to said high speed DC scanning the remaining trunks in said set of trunks to detect said signal on said calling trunk to thereby identify the calling trunk, instructing said remote unit via said data link to connect said calling line corresponding to said calling trunk to said intra-link, identifying said called trunk and for instructing said remote unit via said data link to connect said called line corresponding to said called trunk to said intra-link, and releasing said called and calling trunks.

Claim 20

Generator and latch detector apparatus connectable to a generator bus common to a plurality of trunks in a telephone system wherein connecting said bus draws current in relation to the number of trunks to which it is connected, comprising a current source connected to said bus, means for detecting current flow in said bus, said means comprising a transistor having its emitter collector path connected between said bus and resistor means grounded at the far end, said transistor having a DC voltage applied to its base, whereby said transistor ceases to conduct when current flows in said bus thereby changing the voltage potential at said resistor means, and means for applying a detectable signal to said bus, said means comprising square wave oscillator means, a transistor having its emitter base path connected between said bus and ground and having the output of said oscillator means applied to its base whereby said transistor operates as a saturated switch to ground said bus during one half-cycle of square wave signal.

Claim 21

Generator and latch detector apparatus connectable to a generator bus common to a plurality of trunks in a telephone system wherein connecting said bus draws current in relation to the number of trunks to which it is connected, comprising a current source connected to said bus, means for detecting current flow in said bus, said means comprising a transistor having its emitter collector path connected between said bus and resistor means grounded at the far end, said transistor having a DC voltage applied to its base, whereby said transistor ceases to conduct when current flows in said bus thereby changing the voltage potential at said resistor means, and means for applying a detectable signal to said bus, said means comprising square wave oscillator means, a transistor having its emitter base path connected between said bus and ground and having the output of said oscillator means applied to its base whereby said transistor operates as a saturated switch to ground said bus during one half-cycle of square wave signal.

Claim 22

The combination of claim 17 further comprising means for detecting current flow in said bus exceeding a predetermined amount indicating connecTion of said bus to more than one trunk, said means comprising differential amplifier means for comparing the voltage on said bus to a fixed DC voltage, said DC voltage chosen to be higher than the voltage on said bus when more than one trunk is connected to said bus.