Line card circuit for dual station control

Claim 2

A line card circuit for use with telephone systems including two or more companion key telephone units which are each adapted to have full supervisory control over a telephone circuit common to both key telephone units, and a pair of line conductors connecting each key telephone unit to said telephone circuit through one of a number of companion line card circuits corresponding to the number of companion key telephone units, ringing signals and line current being applied to said key telephone units over said line conductors which are adapted to be interconnected at any of said key telephone units by operation thereof, each said line card circuit comprising: first means including a first relay for energizing said line card circuit in response to either said ringing signals or the flow of said line current through a pair of line conductors coupled thereto; second means for energizing companion line card circuits in response to operation of said first means; third means for enabling ringing at a key telephone unit corresponding to said line card circuit in response to said ringing signals; fourth means responsive to the operation of said corresponding key telephone unit for enabling the presentation of visual operation indicators at said corresponding key telephone unit; and fifth means for enabling the concurrent presentation of said visual operation indicators at companion key telephone units in resPonse to operation of said corresponding telephone unit.

Claim 3

The line card circuit defined by claim 1 wherein said first relay includes first and second coils and a contact, said first coil being adapted to be energized in response to the presence of ringing signals, said second coil being adapted to be energized in response to the presence of line current, said contact being operated in response to the energization of either of said first and second coils.

Claim 4

The line card circuit defined by claim 2, said second means including means responsive to operation of said contact for providing energizing signals to companion line card circuits.

Claim 5

The line card circuit defined by claim 1 wherein said third means includes a second relay and said fourth means includes a third relay, said line card circuit further comprising sixth means including said second and third relays for connecting an impedance between said pair of line conductors coupled thereto to have said pair of line conductors maintained in a hold condition.

Claim 6

The line card circuit defined by claim 4 further comprising means for maintaining said third relay, once energized, in an energized condition for as long as said corresponding key telephone unit is operated.

Claim 7

The line card circuit defined by claim 1, said first means further including a rectifier connected between said pair of line conductors coupled thereto for causing operation of said first relay in response to the presence of said ringing signals.

Claim 8

The line card circuit defined by claim 1, wherein voice signals are applied to said pair of line conductors coupled thereto when said key telephone unit corresponding to said line card circuit is used, said first relay including a first coil operatively connected between said pair of line conductors coupled thereto and a second coil connected in one of said pair of line conductors coupled thereto, said first coil being connected to be energized in response to the application of ringing signals, said second coil being energized by said flow of line current.

Claim 9

The line card circuit defined by claim 6 further including means for rendering said second coil insensitive to said voice signals.

Claim 10

The line card circuit defined by claim 1, said second means including means connected to said first means for providing an energizing signal to companion line circuits in response to operation of said first means.

Claim 11

The line card circuit defined by claim 1, said first means including means for providing a status signal to said companion line card circuits in response to the operational status of said corresponding key telephone unit.

Claim 12

The line card circuit defined by claim 1, further including means for energizing said line card circuit in response to the application thereto of energizing signals from a companion line card circuit.

Claim 13

A telephone line circuit for use with a key telephone system including two or more companion key telephones which are each intended to mutually have full supervisory control over the key telephone system, each key telephone being connected to a central facility via a line circuit and a pair of line conductors that are parallel connected to said central facility, each key telephone having a hold button, said key telephone system having a ringing condition during which ringing signals are simultaneously applied to the line conductors of the companion key telephones, a seize condition characterized by the line conductors of at least one key telephone being interconnected by operation of the key telephone corresponding thereto, and a hold condition characterized by the connection of a holding impedance across the line conductors of each companion key telephone in response to operation of the hold button on at least one key telephone, line current being applied to said line conductors of an operated key telephone during said seize and hold conditions, a telephone line circuit comprising: ringing means for controlling ringing at a key telephone connected theReto; a pair of line leads corresponding to, and adapted to be connected in, the pair of line conductors for said key telephone; first means for detecting ringing signals applied to said line conductors during said ringing condition and for controlling said ringing means to provide ringing at said key telephone connected thereto, said first means being connected between said pair of line leads; second means for detecting the flow of line current in said pair of line leads during said seize and hold conditions to control the ringing means to prevent ringing at said key telephone connected thereto, said second means connected in one of said pair of line leads; and third means adapted to be connected to the telephone line circuits of companion key telephones for detecting any seize and hold conditions produced by operation of a companion key telephone.

Claim 14

A telephone line circuit for use with a key telephone system including two or more companion key telephones which are each intended to mutually have full supervisory control over the key telephone system, each key telephone being connected to a central facility via a line circuit and a pair of line conductors that are parallel connected to said central facility, each key telephone having a hold button, said key telephone system having a ringing condition during which ringing signals are simultaneously applied to the line conductors of the companion key telephones, a seize condition characterized by the line conductors of at least one key telephone being interconnected by operation of the key telephone corresponding thereto, and a hold condition characterized by the connection of a holding impedance across the line conductors of each companion key telephone in response to operation of the hold button on at least one key telephone, line current being applied to said line conductors of an operated key telephone during said seize and hold conditions, a telephone line circuit comprising: ringing means for controlling ringing at a key telephone connected theReto; a pair of line leads corresponding to, and adapted to be connected in, the pair of line conductors for said key telephone; first means for detecting ringing signals applied to said line conductors during said ringing condition and for controlling said ringing means to provide ringing at said key telephone connected thereto, said first means being connected between said pair of line leads; second means for detecting the flow of line current in said pair of line leads during said seize and hold conditions to control the ringing means to prevent ringing at said key telephone connected thereto, said second means connected in one of said pair of line leads; and third means adapted to be connected to the telephone line circuits of companion key telephones for detecting any seize and hold conditions produced by operation of a companion key telephone.

Claim 15

The telephone line circuit defined by claim 12 further comprising holding means for producing a hold condition, said holding means including: a holding impedance; and first and second switches connected in series with the holding impedance, the first and second switches serving to connect the holding impedance between said pair of line leads when both first and second switches are operated.

Claim 16

The telephone line circuit defined by claim 13, said third means including means for detecting initiation of a hold condition by any of the companion key telephones in said key telephone system to have said holding means responsive to operation of each of the companion key telephones in said system.

Claim 17

The telephone line circuit defined by claim 14, said first means including: ringing signal detector means for detecting said ringing signals applied to said line conductors; and a first relay, operated by said ringing signal detector means for controlling said ringing means to provide ringing at said key telephone connected thereto, said first relay also operated in response to operation of the hold button for operating the first switch of the holding means; said second means including: line current detector means for detecting the flow of line current in said pair of line leads, and a second relay operated by said line current detector means for controlling said ringing means to prevent ringing at said key telephone connected thereto and for operating the second switch of the holding means, whereby the hold condition is only produced by concurrent operation of both first and second relays.

Claim 18

The telephone line circuit defined by claim 15, said third means further including means for detecting the operation of said line current detector means of any telephone line circuit in said key telephone system to have said second relay operated to control said ringing means in response to the flow of line current being detected in any of the pair of line leads included in companion telephone line circuits.

Claim 19

The telephone line circuit defined by claim 16 wherein said key telephone system also includes a ringer and a power source adapted to be controllably interconnected through said ringing means to provide a ringing at a key telephone connected thereto, said ringing means including: a ringing conductor for controllably interconnecting the ringer and the power source; and third and fourth switches connected in series in said ringing conductor for individually completing or breaking the continuity of the ringing conductor, said third switch being operated by said first relay to complete the continuity of said ringing conductor to allow interconnection of said ringer and power source by the ringing conductor, said fourth switch being operated by said second relay to break the continuity of the ringing conductor to prevent interconnection of the ringer and power source by the ringing conductor.

Claim 20

The telephone line circuit defined by claim 17, said line current detector means including a third relay having first and second relay coils of which a first coiL is connected in one of said pair of line leads to be operated by the flow of line current in said line leads, said third relay releasing the telephone system from said hold condition in response to a polarity reversal across said line conductors.

Claim 21

The telephone line circuit defined by claim 18, said ringing signal detector means including said third relay and a rectifier connected between said pair of line leads for causing operation of said third relay in response to said ringing signals.

Claim 22

A telephone line circuit for use with key telephone systems including two or more key telephones each equipped with a telephone line circuit and which mutually have full supervisory control over each other, visual and audio indicators indicative of such supervisory control being simultaneously presented at each key telephone, said telephone line circuit comprising: detector means for detecting the operation of any key telephone in said key telephone system, said detector means enabling presentation of indicator signals representative of the status of such operation of any key telephone, the detector means of all corresponding telephone line circuits in said system being adapted to be interconnected.

Claim 23

A telephone line circuit for use with key telephone systems including two or more key telephones each equipped with a telephone line circuit and which mutually have full supervisory control over each other, visual and audio indicators indicative of such supervisory control being simultaneously presented at each key telephone, said telephone line circuit comprising: detector means for detecting the operation of any key telephone in said key telephone system, said detector means enabling presentation of indicator signals representative of the status of such operation of any key telephone, the detector means of all corresponding telephone line circuits in said system being adapted to be interconnected.

Claim 24

The telephone line circuit defined by claim 20 wherein said key telephones are operated to place said telephone system in a seize or hold condition, said detector means including: first means for receiving a ground signal for the duration of any seize condition effected by operation of a key telephone in said system; and second means for receiving a negative battery signal for the duration of any seize or hold condition effected by operation of a key telephone in said system.

Claim 25

A telephone line circuit for use in a telephone system including two or more key telephones each of which is equipped with hold and line buttons, each key telephone being connected via one of said telephone line circuits to a central facility by a pair of line conductors, said key telephone system having a ringing condition during which ringing signals are transmitted from said central facility to each key telephone via said line conductors, a seize condition characterized by a pair of line conductors being interconnected by operation of a key telephone connected thereto, and a hold condition characterized by the connection of a holding impedance between a pair of line conductors in response to operation of the hold button of the key telephone connected thereto, said telephone line circuits operating to permit each key telephone included in said system to exercise full control of visual and/or audio ring, seize and hold indicators which are operated at each key telephone to respectively indicate said ring, seize and hold conditions, said telephone line circuit comprising: first means for causing actuation of said seize indicators at the key telephone connected to the telephone line circuit in response to a seize condition implemented at any key telephone in said telephone system; and second means for causing actuation of said hold indicators at the key telephone connected to the telephone line circuit in response to a hold condition implemented by operation of any key telephone in said telephone system.

Claim 26

A telephone line circuit for use in a telephone system including two or more key telephones each of which is equipped with hold and line buttons, each key telephone being connected via one of said telephone line circuits to a central facility by a pair of line conductors, said key telephone system having a ringing condition during which ringing signals are transmitted from said central facility to each key telephone via said line conductors, a seize condition characterized by a pair of line conductors being interconnected by operation of a key telephone connected thereto, and a hold condition characterized by the connection of a holding impedance between a pair of line conductors in response to operation of the hold button of the key telephone connected thereto, said telephone line circuits operating to permit each key telephone included in said system to exercise full control of visual and/or audio ring, seize and hold indicators which are operated at each key telephone to respectively indicate said ring, seize and hold conditions, said telephone line circuit comprising: first means for causing actuation of said seize indicators at the key telephone connected to the telephone line circuit in response to a seize condition implemented at any key telephone in said telephone system; and second means for causing actuation of said hold indicators at the key telephone connected to the telephone line circuit in response to a hold condition implemented by operation of any key telephone in said telephone system.

Claim 27

The telephone line circuit defined by claim 22, said first means including a relay adapted to be connected to the line button of each of the key telephones in said system to be energized by the operation of any of said line buttons.

Claim 28

The telephone line circuit defined by claim 22, said second means including a relay connected to be energized whenever a hold condition is implemented by operation of any key telephone in said system.

Claim 29

The telephone line circuit defined by claim 22 wherein said first means includes a first relay that is connected to be energized for the duration of any seize condition produced by operation of a key telephone in said system, and said second means includes a second relay that is connected to be energized for at least the duration of any hOld condition produced by operation of a key telephone in said system.