Exclusionary device for coupling plural telephonic devices to a single central office trunk
AssigneeTelecommunication Concepts, Inc.
InventorDonald J. Ryan
Life of this patent
Estimating the term…
Abstract
A controller couples a modem or facsimile device to a telephone trunk or line and also connects another instrument or communications device to the same line so that the line can be shared without danger of the two devices interfering with one another. The line is divided into separate branches to connect to the two devices. Each branch has a line relay that senses line current in the tip and ring conductors of the respective branch when line current is present. A holding feature accommodates dial pulse interruptions in the line current and/or pulse signalling.
Claims9
A line controller for automatically isolating first and second separate telephone line terminal devices that share a common telephone trunk line, comprising,
- input means for coupling to tip and ring conductors of said telephone trunk line, and dividing the same into first and second branches which respectively connect to said first and second devices;
- first line isolation means for cutting off the second device from the second branch when line current appears on the first branch to indicate that the first device has assumed an off-hook condition;
- and
- second line isolation means for cutting off the first device from the first branch when line current appears on the second branch to indicate that the second device has assumed an off-hook condition;
- wherein said first and second line isolation means each include a line relay device having a tip coil connected in series in the tip conductor of the associated branch and a ring coil connected in series in the ring conductor of said associated branch, and normally-closed tip and ring contacts actuated by the associated tip and ring coils and connected in series in the tip and ring conductors of the other of the first and second branches.
A line controller for automatically isolating a telephone trunk that is shared by first and second separate telephone line terminal devices, and which can accommodate either tone dialing or pulse dialing;
- comprising
- input means for coupling to tip and ring conductors of said telephone trunk line and dividing the same into first and second branches which respectively connect to said first and second devices;
- first line current sensing means for sensing d.c. line current on at least one of the tip and ring conductors of the first branch;
- second line current sensing means for sensing d.c. line current on at least one of the tip and ring conductors of the second branch;
- a source of d.c. power having positive and negative d.c. outputs;
- a first holding circuit that includes a first holding relay coil and a switching element coupled to series therewith across said d.c. power source with the switching element having an actuating element, a control circuit connected across said power source outputs that includes a first switch device that changes from a normal to an actuated state in accordance with the sensing of d.c. line current by the first line current sensing means when said d.c. current appears on said first branch, and a time constant circuit connected in series with the first switch device and having an output coupled to the actuating electrode of the associated switching element to energize the first holding relay coil and to hold continue energizing the same if said first switching device reverts to its normal state for less than a predetermined period of time to accommodate pulse dialing interruptions in said d.c. line current;
- a second holding circuit that includes a second holding relay coil and a switching element coupled in series therewith across said d.c. power source outputs with the switching element having an actuating element, and a control circuit coupled across said power source outputs that include a second switch device that changes from a normal to an actuated state in accordance with the sensing of d.c. line current by the second line current sensing means when said d.c. line current appears on said second branch, and a time constant circuit connected in series with said second switch device and having an output coupled to the actuating electrode of the associated switching element to energize said second holding relay coil and to continue energizing the same if said second switch device reverts to its normal state for less than a predetermined period of time to accommodate pulse dialing interruptions in said d.c. line current;
- first normally-closed line switching means disposed in at least one of the tip and ring conductors of the first branch and actuated to an open condition by the second holding relay coil;
- and
- second normally-closed line switching means disposed in at least one of the tip and ring conductors of the second branch and actuated to an open condition by the first holding relay coil.
Dependencies are inferred from the claim text.