Apparatus for controlling and indicating the integrity of the connection of telephone subscribers to a switching system

Claim 1

In a switching system including a digital network, at least one telephone subscriber connected to said switching via a first pair of leads, said first pair of leads connected to said digital network via a second and a third pair of leads, the improvement comprising: circuit means for balancing said connection of said first pair of leads to said second and third pair of leads and said circuit means connected via said first pair of leads to said telephone subscriber and connected via said second and third pair of leads to said digital network; said circuit means including a first subcircuit of a first characteristic and second subcircuit of a second characteristic, said first subcircuit connected to said circuit means and alternatively, said second subcircuit connected to said circuit means; CPU means for controlling and storing data; detection means for determining the status of said first pair of leads, said detection means connected between said first pair of leads and said CPU means, said detection means operated in response to said CPU means to measure the impedance of said first pair leads and to transmit said measurement to said CPU means for storage: network means for simulating said first pair of leads connected to said circuit means and to said CPU means, said network means operated in response to said CPU means selectively to connect a termination of a first characteristic to said circuit means and alternately to connect a termination of a second characteristic to said circuit means; test means for injecting a first signal and measuring a second signal, said test means connected through said digital network to said circuit means via said second and third pair of leads, said test means further connected to said CPU means, said test means operated in response to said CPU means to transmit said first signal and to receive said second signal and said test means further operated to transmit said second signal to said CPU means; said network means operated in response to said CPU means to connect said termination of said first characteristic to said circuit means and said test means operated in response to said CPU means to transmit said first signal to said circuit means and transmit said received second signal to said CPU means, and alternately, said network means operated in response to said CPU means to connect said termination of said second characteristic to said circuit means and said test means further operated in response to said CPU means to transmit said first signal to said circuit means and transmit said received second signal to said CPU means; and said CPU means operated in response to each of said transmitted second signals to compare each of said second signals to detect said connection of said first subcircuit to said circuit means in order to match said first characteristic subcircuit to said first pair of leads and alternatively to detect said connection of said second subcircuit to said circuit means in order to match said second characteristic subcircuit to said first pair of leads.