Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
337 words
In a telephone set of the type having, an off-hook switch, and a key operated control for selecting a line circuit in common with other such telephone sets, said line circuit having a control wire corresponding thereto, the improvement being an exclusion circuit comprising: a. a bistable circuit comprising a pair of transistors having their input and output terminals cross-coupled to provide feedback for holding said bistable circuit in a stable state, and a capacitor connected across the input of a first of said transistors, said bistable circuit being connected via said off-hook switch to a source of power whereby said capacitor causes said bistable circuit to always assume upon initial application of power thereto a first stable state wherein said second transistor conducts and said first transistor is cut off, b. switch control means comprising a relay connected in the output circuit of said second transistor and responsive thereto for controlling first and second switches to cause said first and second switches to switch from their respective normal positions to their respective alternate positions when said bistable circuit is in said first stable state, c. said first switch means in its normal position being connected between said control wire and a reference potential via said off-hook switch, and in its alternate position being connected between said control wire and a trigger input to said bistable circuit, and d. said second switch means in its normal position being connected between said line circuit via said key operated control and a speech network for said set, and in its alternate position disconnecting said line circuit via said key operated control, whereby a non-reference potential on said control wire at the time of switching of said first switch causes said bistable circuit to assume its second stable state, and whereby a reference potential on said control wire at the time of switching of said first switch keeps said bistable circuit in its first stable state thereby to disconnect said speech network of the telephone set from said line circuit.
Claim 2
Dependent Claim
337 words
In a telephone set of the type having, an off-hook switch, and a key operated control for selecting a line circuit in common with other such telephone sets, said line circuit having a control wire corresponding thereto, the improvement being an exclusion circuit comprising: a. a bistable circuit comprising a pair of transistors having their input and output terminals cross-coupled to provide feedback for holding said bistable circuit in a stable state, and a capacitor connected across the input of a first of said transistors, said bistable circuit being connected via said off-hook switch to a source of power whereby said capacitor causes said bistable circuit to always assume upon initial application of power thereto a first stable state wherein said second transistor conducts and said first transistor is cut off, b. switch control means comprising a relay connected in the output circuit of said second transistor and responsive thereto for controlling first and second switches to cause said first and second switches to switch from their respective normal positions to their respective alternate positions when said bistable circuit is in said first stable state, c. said first switch means in its normal position being connected between said control wire and a reference potential via said off-hook switch, and in its alternate position being connected between said control wire and a trigger input to said bistable circuit, and d. said second switch means in its normal position being connected between said line circuit via said key operated control and a speech network for said set, and in its alternate position disconnecting said line circuit via said key operated control, whereby a non-reference potential on said control wire at the time of switching of said first switch causes said bistable circuit to assume its second stable state, and whereby a reference potential on said control wire at the time of switching of said first switch keeps said bistable circuit in its first stable state thereby to disconnect said speech network of the telephone set from said line circuit.
Claim 3
Dependent Claim
89 words
The telephone set as claimed in claim 1 wherein said first switch means has a fixed terminal and a movable terminal, said fixed terminal being connected via a diode and said key operated control to said control line, said movable terminal in the normal position of said switch being connected to one terminal of said off-hook switch, the other terminal of said off-hook switch being connected to a reference potential, said movable terminal in the alternate position of said switch being connected to the input of said first transistor.