Ring control circuit

Claim 2

A ring trip control circuit for a telephone system in which the system has a source for transmitting AC ringing signals to a called line, a ring trip relay for disconnecting the ringing signals from the called line responsive to the called line going off-hook and answer supervision means responsive to the called line going off-hook, the ring trip control circuit comprising means for sensing ringing current applied to a predetermined called line, means responsive to sensed ringing current to said last-mentioned line for simulating an off-hook condition for completing a direct current path to the ring trip relay and thereby operate the ring trip relay to disconnect the ringing source from the ring control circuit, contacts on said ring trip relay in a completed path to said simulating means, said contacts opening said completed path on energization of said relay, said simulating means responsive to operation of said relay for preventing operation of the answer supervision means by opening a path to said answer supervision means before operation thereof.

Claim 3

A circuit as claimed in claim 1, wherein said sensing means comprises means for rectifying said ringing signals, and said simulating means including switching means responsive to rectified ringing signals for closing a direct path from a bias source to said ring trip relay, and including means for biasing said switching means in its operated state between ringing signals.

Claim 4

A circuit as claimed in claim 2, wherein said switching means comprises an SCR with switching time in the nature of microseconds and said answer supervision means comprises an electromechanical member having switching times on the order of milliseconds.

Claim 5

A ring trip control circuit for a telephone system having a source of AC ringing signals with at least one switching control circuit in said system adapted to access a called line to apply ringing signals from the source to a called line, the switching control circuit being equipped with a ring trip relay for disconnecting the ringing signals from the called line responsive to the called line going off-hook and an answer supervision relay normally operative over a closed loop through the called line responsive to an off-hook condition to signal call completion, said ring trip control circuit adapted to be coupled between a predetermined line and said switching control circuit and comprising means for rectifying the ringing current applied to said predetermined line when called, means responsive to the voltage of the rectified current signals reaching a threshold level for operating a switching member, said switching member on operation causing operation of the ring trip relay to disconnect the ringing source from the called line, a path for maintaining said switching means operated, said switching means responsive to a momentary interruption of its maintaining path during operation of said ring trip relay for opening said switching means maintaining path, said switching means included in an operating path to said answer supervision relay and responsive immediately to the opening of said switching means maintaining path to shut off for preventing operation of the answer superVision relay.

Claim 6

A ring trip control circuit for a telephone system having a source of AC ringing signals with at least one switching control circuit in said system adapted to access a called line to apply ringing signals from the source to a called line, the switching control circuit being equipped with a ring trip relay for disconnecting the ringing signals from the called line responsive to the called line going off-hook and an answer supervision relay normally operative over a closed loop through the called line responsive to an off-hook condition to signal call completion, said ring trip control circuit adapted to be coupled between a predetermined line and said switching control circuit and comprising means for rectifying the ringing current applied to said predetermined line when called, means responsive to the voltage of the rectified current signals reaching a threshold level for operating a switching member, said switching member on operation causing operation of the ring trip relay to disconnect the ringing source from the called line, a path for maintaining said switching means operated, said switching means responsive to a momentary interruption of its maintaining path during operation of said ring trip relay for opening said switching means maintaining path, said switching means included in an operating path to said answer supervision relay and responsive immediately to the opening of said switching means maintaining path to shut off for preventing operation of the answer superVision relay.