Automatic electronic disconnector for subscriber terminal equipment
First Claim
1. An electronic disconnector circuit means for automatically disconnecting a subscriber'"'"'s first telephonic terminal device from a subscriber'"'"'s telephonic two wire loop circuit when a second subscriber'"'"'s terminal device is taken off-hook with the first terminal device in an off-hook mode, said disconnector circuit means comprising:
- a. an input terminal for connecting to a first line of the subscriber'"'"'s two wire loop circuit and an output terminal for connecting to an input terminal of said first terminal device, said first terminal device having a first terminal device output terminal connected to a second line of said two wire loop circuit, said disconnecting circuit means and said first terminal device thereby being serially connected between said first and second lines of the two wire loop circuit,b. a current sensing means connected serially with a line disconnecting means between said input and output terminals, and a voltage sensing means connected in parallel with said current sensing means, said voltage sensing means for detecting a voltage drop across the current sensing means and turning the current sensing means on at a predetermined voltage level thereby allowing current to flow through the current sensing means and the first terminal device from the loop circuit, said current sensing means for sensing and monitoring flow of current through the first terminal device and for activating the line disconnecting means to turn off current flow to the first terminal device when said current flow is reduced below a pre-determined level resulting when said second terminal device is taken off-hook, said second terminal device being connected across from said first line to said second line and in parallel with said serially connected disconnector circuit means and said first terminal device, and when said second terminal device is returned to an on-hook mode, said current sensing means senses current flow and said first terminal device is again connected in the loop circuit.
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Accused Products
Abstract
An electronic circuit means for automatically disconnecting an off-hook subscriber'"'"'s first telephonic signal sending and receiving terminal device which is in an off-hook mode when a second terminal device is taken off-hook. The disconnector circuit means has voltage sensing means, current sensing means and line disconnecting means. The voltage sensing means senses a voltage across the current sensing means and when at a pre-determined level turns the current sensing means on allowing current to flow through the first terminal device. When the second terminal device is taken off-hook, the voltage across the loop circuit drops and current flow through the current sensing means drops. When the current drops to a pre-determined value, the current sensing means actuates the line disconnecting means and shuts off the current flow through the first terminal device.
61 Citations
6 Claims
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1. An electronic disconnector circuit means for automatically disconnecting a subscriber'"'"'s first telephonic terminal device from a subscriber'"'"'s telephonic two wire loop circuit when a second subscriber'"'"'s terminal device is taken off-hook with the first terminal device in an off-hook mode, said disconnector circuit means comprising:
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a. an input terminal for connecting to a first line of the subscriber'"'"'s two wire loop circuit and an output terminal for connecting to an input terminal of said first terminal device, said first terminal device having a first terminal device output terminal connected to a second line of said two wire loop circuit, said disconnecting circuit means and said first terminal device thereby being serially connected between said first and second lines of the two wire loop circuit, b. a current sensing means connected serially with a line disconnecting means between said input and output terminals, and a voltage sensing means connected in parallel with said current sensing means, said voltage sensing means for detecting a voltage drop across the current sensing means and turning the current sensing means on at a predetermined voltage level thereby allowing current to flow through the current sensing means and the first terminal device from the loop circuit, said current sensing means for sensing and monitoring flow of current through the first terminal device and for activating the line disconnecting means to turn off current flow to the first terminal device when said current flow is reduced below a pre-determined level resulting when said second terminal device is taken off-hook, said second terminal device being connected across from said first line to said second line and in parallel with said serially connected disconnector circuit means and said first terminal device, and when said second terminal device is returned to an on-hook mode, said current sensing means senses current flow and said first terminal device is again connected in the loop circuit. - View Dependent Claims (2, 3)
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4. An electronic disconnector circuit means for automatically disconnecting a subscriber'"'"'s first telephonic terminal device from a subscriber'"'"'s telephonic two wire loop circuit when a second subscriber'"'"'s terminal device is taken off-hook with the first terminal device in an off-hook mode, said disconnector circuit comprising an input terminal for connecting to either of the first or second lines of the said two wire loop circuit, having a full wave diode bridge rectifier means attached thereto at a bridge input terminal, said bridge having a bridge output terminal for connecting to an input terminal of a first telephonic terminal device, said bridge further having positive and negative terminals and having a cathode of a zener diode and a relay means movable switching contact terminal means connected to said positive bridge terminal, said zener diode having an anode connected to a first end of an electromagnetic relay coil, said coil having a second end connected to the bridge negative terminal and having intermediate the first and second coil ends a connection to a stationery relay switch contact, said movable switching contact operable by said relay coil when current flows therethrough to close said relay contacts, said switching contact having mechanical spring means for maintaining the contacts in an open position when said relay coil is not energized;
- when a central office AC bell ringing signal is applied to the loop circuit, the zener diode permits current to flow therethrough thereby energizing the relay and closing the contacts and at the same time actuating the serially connected first terminal device into an off-hook mode thereby allowing DC current to flow through the loop circuit and through the disconnector and the first terminal device, this shorts out the zener diode and allowing DC current to flow through the loop circuit, a relay coil contact holding section between said stationary contact connection to said coil and said second end of said coil producing a switched contact holding electromagnetic force thereby holding the switched contact in a closed position;
when a second terminal device connected parallelly across the two wire loop circuit with respect to the serially connected disconnector circuit means and the first terminal device is taken off-hook, a loop voltage drops and current flowing through the relay coil drops below a current value sufficient to produce the required electromagnetic holding force and the switched contact opens thereby returning the first terminal device to an on-hook mode.
- when a central office AC bell ringing signal is applied to the loop circuit, the zener diode permits current to flow therethrough thereby energizing the relay and closing the contacts and at the same time actuating the serially connected first terminal device into an off-hook mode thereby allowing DC current to flow through the loop circuit and through the disconnector and the first terminal device, this shorts out the zener diode and allowing DC current to flow through the loop circuit, a relay coil contact holding section between said stationary contact connection to said coil and said second end of said coil producing a switched contact holding electromagnetic force thereby holding the switched contact in a closed position;
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5. An electronic disconnector circuit means for automatically disconnecting and isolating from a subscriber'"'"'s telephonic two wire loop circuit a subscriber'"'"'s first telephonic terminal device when a subscriber'"'"'s second telephonic terminal device is taken off-hook with said first terminal device being off-hook comprising:
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a. first and second disconnector input terminals for connection to first and second loop lines respectively of said loop circuit, b. first and second disconnector output terminals corresponding respectively with said first and second disconnector input terminals, said output terminals for connection respectively to input and output terminals of said first telephonic terminal device, c. a first current sensing means having first current sensing means input terminal connected to said first disconnector input terminal and a first current sensing means output terminal connected to a line disconnecting means first relay switching contact member, d. a second current sensing means having a second current sensing means input terminal connected to said second disconnector input terminal and a second current sensing means output terminal connected to a line disconnecting means second relay switching member, e. a voltage sensing means having a voltage sensing means input terminal connected to the output terminal of the first current sensing means and having a voltage sensing means output terminal connected to the output terminal of the second current sensing means, f. a line disconnecting relay means having said first and second relay switching contact members for switching between first and second sets of relay stationary contacts respectively, said switching contact members operable by spring means for making contact between the first switching contact member and a first set first stationary contact and between the second switching contact member and a second set first stationary contact, thereby maintaining said first and second switching contacts normally closed with first and second set first stationary contacts respectively, said first and second switching contacts further operable in opposition to said spring means by an electromagnetic relay coil when current flows therethrough for making contact between the first switching contact member and a first set second stationary contact and between the second switching contact member and a second set second stationary contact, said second stationary contacts having a current sustaining resistor member connected therebetween for permitting a limited amount of current flow therethrough; when the first and second disconnector input terminals are connected respectively to first and second lines of the subscriber'"'"'s two wire loop circuit and the first and second disconnector output terminals are connected respectively to the first telephonic terminal device input and output terminals, and when an AC bell ringing signal is applied at a central office, the first terminal device is activated and loop DC current flows, the current sensing means senses the current and turns on the voltage sensing means, thereafter when a second telephonic terminal device connected across the two wire loop circuit is taken off-hook, loop circuit voltage is thereby reduced, the voltage sensing means senses this reduction in loop circuit voltage and activates the line disconnecting relay means thereby opening the lines to the first terminal device;
when the second terminal device is returned to an on-hook mode, the loop circuit voltage is increased and the relay member is de-energized returning the first terminal device to a line connected condition, the resistor member is for maintaining current flow through the current sensor means thereby maintaining the voltage sensor means in an on condition while the first terminal device is disconnected from the two wire loop circuit. - View Dependent Claims (6)
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Specification