Subscriber interface for a fiber optic communications terminal

Multiplex communications – Pathfinding or routing – Through a circuit switch

Reexamination Certificate

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Reexamination Certificate

active

06333930

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates generally to a telephone communications terminal, and more specifically, to a terminal adapted to interconnect a large number of telephone circuits of various types with a high bandwidth communication link.
In cases where a large number of individual telephone channels need to be provided between two geographical locations, it is common to multiplex a number of such channels on a single wide bandwidth circuit that extends between the locations. Multiplexing equipment is then provided at each location. This is done primarily to reduce the cost of providing transmission link for a large number of channels between the two locations.
An example is a loop carrier system provided between a large telephone company central office and a concentration of individual telephone subscribers located at least several miles away. A high bandwidth communications circuit is provided from the central office to the customer location, with a multiplexing terminal at each end. The use of a fiber optic transmission media between the terminals has an advantage over the use of a single electrical circuit in its greater bandwidth; that is, optical fiber systems can carry a much greater number of individual telephone channels. The channels are time multiplexed onto a single optical fiber transmission medium by providing repetitive time slots in sequence that are dedicated to each channel. Each terminal, therefore, provides for inserting signals from each channel being transmitted into its unique fiber optic time slot, and directs each received time slot to the correct individual telephone circuit. Each terminal includes a time slot interchanger that allows control of which end user telephone channels are assigned to which time slots in the fiber optic transmission system.
Each such terminal must be capable of interconnecting with any one of several standard types of end user telephone circuits. A most common type is a circuit carrying a single telephone channel which is connected to a standard telephone instrument, computer terminal modem, and the like. Another common circuit, long designated as a T1 carrier system, carries 24 individual telephone channels. The T1 circuit eventually terminates each of its channels with a telephone subscriber. Since such systems are already widely in use, it is necessary to be able to connect them with the fiber optic trunk line. Other standards providing 12, 48 and 96 channels on a single wired telephone circuit also exist and must be connectable to such a communications terminal.
Therefore, it is a primary object of the present invention to provide a terminal system and components thereof that provides an ability for easily accommodating any of a wide variety of existing telephone subscriber circuits while utilizing the full bandwidth capability of the system.
SUMMARY OF THE INVENTION
This and additional objects are accomplished by the present invention wherein, briefly and generally, a communications terminal adapted to be connected with a trunk having a wide bandwidth for accommodating a large number of individual communication channels is provided with a backplane of a large number of identical circuit card slot connectors which accommodate any of several types of circuit cards that are specifically designed to interface with the various types of subscriber (customer) wired telephone circuits, some of which are discussed above. A large number of buses interconnect the card connectors with a terminal control system and time slot interchanger. Each connector includes a primary set of conductors in a given position, and one or more sets of secondary conductors. The primary set of conductors of each backplane connector is connected with a unique one of the buses. Each bus is also connected with a secondary set of conductors of at least one other circuit card connector.
Each circuit card adapted to be received by the card slot provides connection with at least its primary set of conductors. Each card may use up to the maximum number of communication channels provided on a single bus through that interconnection. The capacity of the buses is made large enough to include the channel capacity of the most common subscriber telephone circuits. But for those situations where additional channels are required, the circuit card for that application additionally interconnects with one or more secondary sets of conductors in order to use any available channel capacity on the buses connected to them. Circuit cards are specifically designed for interfacing with a particular type of customer telephone circuit, and uniquely take advantage of the bandwidth provided at each of the card slots connectors.
Additional objects, advantages and features of the various aspects of the prevent invention will become apparent from the following description of a preferred embodiment thereof, which description should be taken in conjunction with the accompanying drawings.


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J. B. Terry, et al., “Bit-Rate on Demand Subscriber Access”, The International Symposium on Subscriber Loops and Services, Sep. 29, 1986-Oct. 3, 1986, cover page and pp. 193-198.

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