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Telecommunications switch with improved redundancy
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Inventors: Madonna, Robert P.; Eschholz, Siegmar K.; Lynch, John T.;
Assignee: Excel, Inc. (Hyannis, MA)
Primary Examiner: Hsu; Alpus H.
Assistant Examiner:
Attorney, Agent or Firm: Cesari and McKenna, LLP
A programmable telecommunications switch has automatic backup of line cards to provide complete redundancy. The switch has I/O cards which terminate the external telecommunications spans. Each I/O card passes the data from its spans to a line card. When the line card fails, the I/O card switches the data onto an I/O bus which is connected to a standby I/O card. The standby I/O card switches a standby line card into connection with the I/O bus such that the data stream is then serviced by the standby line card. The failed line card may then be removed and replaced. All I/O cards are attached to the I/O bus such that redundancy for all active line cards using the same signalling protocol is provided with a single standby line card. With multiple I/O busses, standby I/O cards and standby line cards, multiple redundancy is possible. Finally, the failure of a single line module of a line card may be handled by switching only the span serviced by that module to a standby line card. Spans from different I/O cards may be serviced by different line modules of a single standby line card, and may be all connected to the same standby line card by the same bus. |
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DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Shown in FIG.
1 is a programmable telecommunications switch 10.
The switch is constructed on circuit boards or "cards" which are located in slots on a passive backplane.
Alternatively, the boards may instead be located within a personal computer in the slots of a motherboard of the computer.
The slots of the backplane contain edge connectors which, when the cards are inserted, provide connection between the cards and the appropriate busses of the switch 10.
When each card is plugged into a slot, conductors on its surface make connection with those busses to which that card needs access.
The busses of the switch include a high level data link control (HDLC) bus 20, a time division multiplexed (TDM) bus 22, an I/O card (I/O) status/control bus 24 and a timing/control bus 26.
A power bus 9 is provided which provides power to all of the cards.
In addition, a pre-charge bus 11 is provided which is a power source that is arranged in the backplane so that when a card is plugged into a slot the card comes into contact with the pre-charge bus 11 first.
This prevents the card being inserted from causing unwanted fluctuations in the power signal of power bus 9, which might disrupt the system if the new board was inserted while the system was operational.
It also allows the card being inserted to receive power before receiving data, so that its internal components are properly initialized.
Both the power bus 9 and the pre-charge bus 11 receive their power from power card 13.
As indicated in FIG.
1, there are actually multiple power cards 13 to provide redundancy if one of them fails.
In the preferred embodiment, there are two power cards 13 and, while both are functioning properly, each supplies one-half of the necessary power to power bus 9 and pre-charge bus 11.
If one of the power cards 13 should fail, then the other card responds by providing all of the required power.
A CPU card 12 is interconnected with digital line cards 34,36,38 and input/output (I/O) cards 40,44,48 which terminate T1, E1 and J1 spans, respectively
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