Communication path fault detector

Claim 2

A circuit for use on a communication connection to detect an undesired condition which trips called station ringing and interferes with a called station answer signal needed for call charging and comprising means responsive to a receipt of a signal signifying a tripping of called station ringing following a receipt of a call for producing a test signal persistent for a prescribed duration, means activated by said test signal for generating a timed interval an expiration of which indicates an undesired condition that interferes with a valid called station answer signal, and means responsive to a receipt of a valid called station answer signal during the persistence of said test signal for deactivating said generating means to arrest a generation of said timed interval prior to said expiration.

Claim 3

The invention of claim 1 wherein said producing means comprises control means activated in response to a receipt of an incoming call and thereafter being deactivated in response to a receipt of a said signal signifying a tripping of called station ringing, and means cooperating with said control means and being responsive to an activation and deactivation of said control means for providing said test signal persistent for said prescribed duration.

Claim 4

The invention of claim 2 wherein said control means includes a first relay activated in response to a receipt of an incoming call and deactivated in response to a receipt of a signal signifying a tripping of called station ringing on said call and a second relay operated in response to an activation of said first relay and having a slow time release subsequently initiated upon a deactivation of said first relay, and wherein said providing means includes contacts of said first and second relays and being effective during a concurrent deactivation of said first relay and said slow time release of said second relay for providing said test signal persistent for said prescribed duration.

Claim 5

The invention of claim 1 wherein said generating means includes a timer operable for initiating said timed interval and progressing toward an expiration of said timed interval, and a bistable switching means responsive to a receipt of said test signal for operating said timer and including means responsive to a receipt of a reset signal for terminating the operation of said timer.

Claim 6

The invention of claim 4 further comprising means activated by said timer upon an expiration of said timed interval for indicating said undesired condition, and means activated by indicating means for subsequently holding said communication connection.

Claim 7

The invention of claim 4 wherein said means for deactivating said generating means includes means responsive to a receipt of said test signal and a valid called station answer signal within a predetermined time period prior to an expiration of said timed interval for supplying said reset signal to said bistable switching means.

Claim 8

The invention of claim 6 wherein said supplying means includes a timing device responsive to a receipt of said test signal for initiating timing of said predetermined time period and subsequently responsive to a termination of said test signal for arresting timing of said time period to control a withholding of said reset signal.

Claim 9

The invention of claim 7 wherein said timing device is further responsive to a receipt of a valid called party answer signal during the persistence of said tesT signal for continuing said timing toward an expiration of said predetermined time period.

Claim 10

The invention of claim 8 wherein said supplying means further includes means activated by said timing device at the expiration of said predetermined time period for supplying said reset signal to said bistable means.

Claim 11

Incoming trunk circuitry for determining a tripping of called station ringing over call connections and an absence of a valid called station answer signal for call charging and comprising switch means activated by an incoming trunk in response to a receipt of an incoming call and subsequently deactivated by said trunk in response to a detection of a tripping of called station ringing, a slow release switch device operated by the activated switch means and slow released upon a deactivation of said switch means, circuit means in said incoming trunk activated in response to a deactivation of said switch means and during the slow release of said switch device for forcing a called party answer signal, said circuit means being further held activated in response to a receipt of a valid called station answer signal, a first timer activatable for generating a timed interval an expiration of which indicates an absence of a valid called station answer signal, bistable means responsive to an activation of said circuit means for switching from a first to a second stable state to activate said timer and having means subsequently responsive to a receipt of a reset signal for resetting said bistable means to said first state for deactivating said timer to arrest further generation of said timed interval, a second timer responsive to said activation of said circuit means for producing a timed period an expiration of which indicates a receipt of a valid called station answer signal, means responsive to an expiration of said timed period for supplying a reset signal to said bistable means, and means operated by said first timer upon an expiration of said timed interval for controlling said incoming trunk to hold call connections to the called station.

Claim 12

Incoming trunk circuitry for determining a tripping of called station ringing over call connections and an absence of a valid called station answer signal for call charging and comprising switch means activated by an incoming trunk in response to a receipt of an incoming call and subsequently deactivated by said trunk in response to a detection of a tripping of called station ringing, a slow release switch device operated by the activated switch means and slow released upon a deactivation of said switch means, circuit means in said incoming trunk activated in response to a deactivation of said switch means and during the slow release of said switch device for forcing a called party answer signal, said circuit means being further held activated in response to a receipt of a valid called station answer signal, a first timer activatable for generating a timed interval an expiration of which indicates an absence of a valid called station answer signal, bistable means responsive to an activation of said circuit means for switching from a first to a second stable state to activate said timer and having means subsequently responsive to a receipt of a reset signal for resetting said bistable means to said first state for deactivating said timer to arrest further generation of said timed interval, a second timer responsive to said activation of said circuit means for producing a timed period an expiration of which indicates a receipt of a valid called station answer signal, means responsive to an expiration of said timed period for supplying a reset signal to said bistable means, and means operated by said first timer upon an expiration of said timed interval for controlling said incoming trunk to hold call connections to the called station.

Claim 13

A called party answer fault detector circuit comprising means responsive to a receipt of a signal signifying a tripping of a called station ringing signal for generating a timed interval, means determining a receipt of a valid called station answer signal during the generation of said timed interval for deactivating said generating means to arrest the generation of said timed interval, and means activated by said generating means upon an expiration of said timed interval for indicating a called party answer fault.

Claim 14

A called party answer fault detector circuit comprising means responsive to a receipt of a signal signifying a tripping of a called station ringing signal for generating a timed interval, means determining a receipt of a valid called station answer signal during the generation of said timed interval for deactivating said generating means to arrest the generation of said timed interval, and means activated by said generating means upon an expiration of said timed interval for indicating a called party answer fault.