Key telephone unit line card

Claim 2

A circuit for use in a key telephone system having a line capable of being in seized and unseized conditions, such line including input conductors on which periodic ring signals occur, comprising means for coupling said circuit to at least one of said input conductors to receive said ring signals, said means for coupling including means electrically isolating said circuit from said at least one of said input conductors for producing isolated signals in response to said ring signals and capacitive means for blocking DC signals on said input conductors from said circuit precluding false production of such isolated signals from noise, extraneous signals and the like on such input conductors, means coupled to said means for coupling for temporarily storing said isolated signals as stored isolated signals, means including selective resistor means for varying the duration for which said stored isolated signals are temporarily stored, logic circuit means coupled to said means for temporarily storing and responsive to said seized and unseized conditions of said line and to said stored isolated signals for producing logic output signals, said logic circuit means including a plurality of NOR gate circuits, and means responsive to said logic output signals for effecting indications of occurrence of said ring signals and of said seized and unseized conditions of said line.

Claim 3

A circuit for use in a key telephone system having a line capable of being in seized and unseized conditions as set forth in claim 1, wherein said means for coupling comprises means for producing electro-magnetic radiation in response to receipt of said ring signals, and said means for producing comprises means responsive to said electromagnetic energy for producing said isolated signals.

Claim 4

A circuit for use in a key telephone system having a line capable of being in seized and unseized condition as set forth in claim 2, wherein said means for producing electromagnetic energy comprises a lamp means for producing light energy and said capacitive means for blocking blocks DC signals from said lamp.

Claim 5

A circuit for use in a key telephone system having a line capable of being in seized and unseized conditions as set forth in claim 3, said ring signals being periodic, having an on time and an off time, and wherein said capacitive means for blocking DC signals blocks the same from said lamp when said ring signals do not occur.

Claim 6

A circuit for use in a key telephone system having a line capable of being in seized and unseized conditions as set forth in claim 1, wherein said means for temporarily storing comprises a capacitor means for storing said isolated signals and said selective resistor means is coupled for varying the rate of discharge of said capacitor means.

Claim 7

A circuit for use in a key telephone system having a line capable of being in seized and unseized conditions as set forth in claim 5, said logic circuit means being directly coupled to said capacitor means, and at least one of said NOR gate circuits being coupled for selectively discharging said capacitor means.

Claim 8

A circuit for use in a key telephone system having a line capable of being in seized and unseized conditions as set forth in claim 1, wherein said means responsive to said logic output signals comprises first and second relay means for operating a plurality of contacts to effect said indication, and first and second transistor means coupled for respectively energizing said first and second relay means in response to said logic output signals.

Claim 9

A circuit for use in a key telephone system having a line capable of being in seized and unseized conditions as set forth in claim 7, one of said relay means being energized by said logic circuit means and said transistor means when said line is in the seized condition, and further comprising light emitting diode means coupled to the latter transistor means for indicating when the latter relay means is energized and means for delaying an indication of said logic circuit means of termination of a seized condition, whereby the existence of a brief unseized condition does not effect a change in said logic circuit means.

Claim 10

A circuit for use in a key telephone system having a line capable of being in seized and unseized conditions as set forth in claim 7, further comprising further relay means coupled in at least one of said input conductors for energization thereby in response to energization of one of said first and second relay means for effecting a change in at least one input signal to said logic circuit means.

Claim 11

A circuit for use in a key telephone system having a line capable of being in seized and unseized conditions as set forth in claim 9, said plurality of contacts being coupled for selectively energizing an interrupter circuit and audio and visual signal producing circuits in response to the energized and de-energized states of said first and second relay means.

Claim 12

A circuit for use in a key telephone system having a line capable of being in seized and unseized conditions as set forth in claim 9, further comprising hold resistor means for maintaining said line in seized condition upon energization of both of said first and second relay means.

Claim 13

A circuit as set forth in claim 1, said NOR gate circuits comprising complementary metal oxide substrate integrated circuits, and zener diode means and current limiting means coupled for providing regulated input power to said NOR gate circuits.

Claim 14

A line card for use in a key telephone system having ring and tip lines on which periodic ring signals occur, comprising an isolation circuit for coupling said line card to at least one of said ring and tip lines while maintaining electric isolation therebetween, a time-out circuit including a capacitor storage means coupled to said isolation circuit for storing isolated signals produced by the latter in response to a received ring signal, and selective resistor means coupled to each other at a common connection and also being individually connectable to said capacitor storage means for discharging the latter, whereby said capacitor storage means effects production of continuous stored isolated signals in response to the periodically varying isolated signals produced by said isolation circuit in respOnse to said periodic ring signals, logic circuit means coupled to said capacitor storage means for producing logic output signals in response to the occurrence of said stored isolated signals and to signals indicative of seized and unseized conditions of said ring and tip lines, said logic circuit means including a plurality of NOR gate circuits, each having respective input terminals and output terminals, at least one of said input terminals being coupled for receipt of said continuous stored isolated signal, and at least another one of said input terminals being coupled for receipt of said signals indicative of said seized and unseized conditions, and the output terminals from at least two of said NOR gate circuits being coupled to produce logic output signals, and first and second relay means responsive to said logic output signals coupled for operating contact elements to indicate occurrence of said ring signals and seized and unseized conditions of said ring and tip lines, at least one of said relay means being coupled for energization of a further relay means coupled in one of said ring and tip lines, said further relay means being coupled for operating contact elements to effect change of at least one input signal to at least one of said NOR gate circuits.

Claim 15

A line card for use in a key telephone system having ring and tip lines on which periodic ring signals occur, comprising an isolation circuit for coupling said line card to at least one of said ring and tip lines while maintaining electric isolation therebetween, a time-out circuit including a capacitor storage means coupled to said isolation circuit for storing isolated signals produced by the latter in response to a received ring signal, and selective resistor means coupled to each other at a common connection and also being individually connectable to said capacitor storage means for discharging the latter, whereby said capacitor storage means effects production of continuous stored isolated signals in response to the periodically varying isolated signals produced by said isolation circuit in respOnse to said periodic ring signals, logic circuit means coupled to said capacitor storage means for producing logic output signals in response to the occurrence of said stored isolated signals and to signals indicative of seized and unseized conditions of said ring and tip lines, said logic circuit means including a plurality of NOR gate circuits, each having respective input terminals and output terminals, at least one of said input terminals being coupled for receipt of said continuous stored isolated signal, and at least another one of said input terminals being coupled for receipt of said signals indicative of said seized and unseized conditions, and the output terminals from at least two of said NOR gate circuits being coupled to produce logic output signals, and first and second relay means responsive to said logic output signals coupled for operating contact elements to indicate occurrence of said ring signals and seized and unseized conditions of said ring and tip lines, at least one of said relay means being coupled for energization of a further relay means coupled in one of said ring and tip lines, said further relay means being coupled for operating contact elements to effect change of at least one input signal to at least one of said NOR gate circuits.

Claim 16

A circuit for use in a key telephone system having a line capable of being in seized and unseized conditions as set forth in claim 13, further comprising means responsive to the polarity of said ring and tip lines at said further relay means for providing an energization voltage therefor.

Claim 17

A circuit for use in a key telephone system having a line capable of being in seized and unseized conditions as set forth in claim 13, further comprising first and second transistor means coupled to said first and second relay means for controlling current through the latter upon production of respective logic output signals.

Claim 18

A circuit for use in a key telephone system having a line capable of being in seized and unseized conditions as set forth in claim 15, further comprising a light emitting diode coupled to one of said transistors for indicating current flow to the relay means coupled thereto.

Claim 19

A line card for use in a key telephone system having ring and tip input conductors and a telephone unit for connection across said input conductors, such telephone unit having a hold circuit, said line card comprising an isolation circuit coupled to said ring and tip input conductors for producing in response to a received periodic ring signal a periodic isolated signal, said isolation circuit including capacitive means for blocking DC signals precluding false production of such periodic isolated signal from noise, extraneous signals and the like on such input conductors, means for storing said periodic isolated signal to produce a stored isolated signal upon the continued occurrence of said periodic ring and isolated signals, a logic circuit comprising a plurality of NOR gate circuits, each having respective input and output terminals, said means for storing being coupled to one input terminal of a first one of said NOR gate circuits, an input circuit for normally producing a first logic signal to the second input terminal of said first NOR gate circuit and to a first input terminal of a second NOR gate circuit, the output terminal of said first NOR gate circuit being coupled to a first input terminal of a third NOR gate circuit, and the second input terminal to said third NOR gate circuit being connected to receive a logic input signal indicative of the connection of said telephone unit across said input conductors or energization of said hold circuit, the latter logic input signal being coupled to the second input terminal of said second NOR gate circuit, said second NOR gate circuit output terminal being connected to the first and second input terminals of a fourth NOR gate circuit and for selectively discharging said means for storing, the output terminals from said third and fourth NOR gate circuits being coupled to respective first and second transistors for controlling current flow therethrough, said first and second transistors being connected to first and second relay means for selectively controlling contact elements to effect production of signals indicative of occurrence of said ring signals, occurrence of said connection of said telephone unit across said input conductors, or occurrence of energization of said hold circuit.

Claim 20

A line card for use in a key telephone system having ring and tip input conductors and a telephone unit for connection across said input conductors, such telephone unit having a hold circuit, said line card comprising an isolation circuit coupled to said ring and tip input conductors for producing in response to a received periodic ring signal a periodic isolated signal, said isolation circuit including capacitive means for blocking DC signals precluding false production of such periodic isolated signal from noise, extraneous signals and the like on such input conductors, means for storing said periodic isolated signal to produce a stored isolated signal upon the continued occurrence of said periodic ring and isolated signals, a logic circuit comprising a plurality of NOR gate circuits, each having respective input and output terminals, said means for storing being coupled to one input terminal of a first one of said NOR gate circuits, an input circuit for normally producing a first logic signal to the second input terminal of said first NOR gate circuit and to a first input terminal of a second NOR gate circuit, the output terminal of said first NOR gate circuit being coupled to a first input terminal of a third NOR gate circuit, and the second input terminal to said third NOR gate circuit being connected to receive a logic input signal indicative of the connection of said telephone unit across said input conductors or energization of said hold circuit, the latter logic input signal being coupled to the second input terminal of said second NOR gate circuit, said second NOR gate circuit output terminal being connected to the first and second input terminals of a fourth NOR gate circuit and for selectively discharging said means for storing, the output terminals from said third and fourth NOR gate circuits being coupled to respective first and second transistors for controlling current flow therethrough, said first and second transistors being connected to first and second relay means for selectively controlling contact elements to effect production of signals indicative of occurrence of said ring signals, occurrence of said connection of said telephone unit across said input conductors, or occurrence of energization of said hold circuit.

Claim 21

A line card as set forth in claim 17, further comprising further relay means coupled in one of said ring and tip lines for energization thereby in response to energization of one of said first and second relay means, said further relay means being coupled for controlling ssid input circuit to effect change in said first logic signal.

Claim 22

A line card as set forth in claim 18, further comprising light emitting diode means coupled to one of said transistor means for indicating current flow through at least one of said first and second relay means indicative of the connection of said telephone unit across said input conductor, whereby operation and energization of said line card is indicated by emission of light from said light emitting diode.

Claim 23

A line card for key telephone systems, such line card including logic circuitry responsive to a ring signal on a telephone line and to the condition of a telephone unit for effecting selective energization of relays to provide for line seizure and for appropriate signal indications of ring signal, line seizure, and hold conditions, the improvement comprising, said logic circuitry including complementary metal oxide substrate integrated circuit logic gates, and zener diode means and current limiting means coupled for providing regulated input power to said logic gates.

Claim 24

A line card for key telephone systems, such line card including logic circuitry responsive to a ring signal on a telephone line and to the condition of a telephone unit for effecting selective energization of relays to provide for line seizure and for appropriate signal indications of ring signal, line seizure, and hold conditions, the improvement comprising, said logic circuitry including complementary metal oxide substrate integrated circuit logic gates, and zener diode means and current limiting means coupled for providing regulated input power to said logic gates.

Claim 25

A line card for key telephone systems as set forth in claim 20, wherein said zener diode means and said current limiting means are connected in series circuit between an input power supply and relative ground potential.