Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Of individual circuit component or element
Reexamination Certificate
2001-05-25
2003-02-18
Oda, Christine (Department: 2858)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Of individual circuit component or element
C324S415000
Reexamination Certificate
active
06522151
ABSTRACT:
FIELD OF THE INVENTION
This invention pertains generally to digital communications over cabled networks, and more particularly to structures and methods for connecting communication systems to the lines of a communications network.
BACKGROUND OF THE INVENTION
Telecommunications employs the transmittal of data over a distance. A given transmission may travel over a common electrical wire, a fiber optic cable, a terrestrial microwave link, or even a satellite link; indeed, most distant transmissions use more than one of these media as they travel from sender to receiver. However, most equipment at the receiving or transmitting end of a signal connects to an electrical wire, usually because of simplicity, cost, and the lower bandwidth requirements of end equipment.
Two types of wires are most commonly used for connecting data lines to end equipment. The first is the twisted-pair conductor (see FIG.
1
), which consists of two thin, insulated electrical conductors
20
,
22
twisted together in a helical fashion. The second is the coaxial conductor (see FIG.
2
), which consists of a single insulated center conductor
24
surrounded by a braided conducting sheath
26
and an outer, insulating protective covering
28
. The twisted-pair conductor enjoys a price advantage over the coaxial conductor. The twisted-pair conductor also occupies less space, such that several twisted pairs can be bundled in a cable roughly the size of one coaxial conductor. The coaxial conductor also has advantages; for example, it is less fragile and better suited for high-bandwidth communications.
Twisted pairs generally operate in a differential mode, while coaxial conductors operate in a single-ended mode. In differential mode, a positive signal change on one wire is coupled with an equally negative signal change on its pair. This differential signal reduces radiated noise from the twisted pair. In contrast, single-ended transmission occurs over a single wire between two devices sharing a common ground connection. With a coaxial cable, the center conductor provides a signal path and the braided sheath is generally tied to the equipment chassis ground. The differential mode of transmission is commonly termed “balanced” because both wires act equally in sending a signal, while the single-ended mode is known as “unbalanced” because a single wire carries the signal.
Equipment suppliers have historically offered either a balanced or an unbalanced connection on a single system. Some suppliers have also offered systems that have dual connection ports, with the customer being responsible for removing a cover from a unit and installing one or more internal jumpers to complete the system configuration.
SUMMARY OF THE INVENTION
With the continued trend towards smaller and more powerful integrated circuits, equipment producers have been able to offer relatively small physical products that can handle a large number of data signal inputs and outputs. These systems may have the added flexibility of being able to interpret or produce data in several formats. With such systems, the panel space available for input and output connections can become a limiting factor in both the size and the flexibility of the product.
It has now been recognized that a need exists for a single system that, while conserving panel space, allows a customer to connect to multiple twisted-pair, multiple coaxial, or even a mix of twisted-pair and coaxial data inputs and outputs as the customer desires. It has also now been recognized that a configurable system not only should be flexible, but preferably should be relatively foolproof; i.e., the customer should not be expected to disassemble a system and properly install 24 jumpers in order to connect 24 inputs and outputs to the system.
In response to this need, the present invention allows connection of either a balanced or unbalanced data connection to a system through a single data port and a single isolation transformer. The system typically supplies, at the port, two transformer contacts connected across a balanced isolation transformer and a third contact connected to ground. A balanced signal is connected to the system using a jack that mechanically engages with the port such that the two balanced signal wires are connected to the two transformer contacts. An unbalanced signal is connected to the system using a similar jack engaged with the same port; however, this jack is wired such that the single unbalanced conductor is connected to one transformer contact, and the conductor shield is connected to both the other transformer contact and the ground contact. This second jack configuration automatically unbalances the system's isolation transformer when the jack is inserted into the data port.
To make the present invention simple for the user, the unbalanced jack is preferably part of a “patch cable” that may be supplied with the system. The patch cable provides the necessary connections to unbalance a system's transformer, while preferably providing a second end with a connector traditionally used with unbalanced cables, such as a BNC connector. This allows a customer little leeway for misconnection—the customer simply connects the jack into the system port, and connects the other end of the patch cable directly to the data line as a traditional unbalanced cable connection.
A related problem solved by the invention is the problem of providing signal and system testing and monitoring for a multiple-data-line system, as test ports also consume panel space. This problem compounds when the customer may connect either balanced or unbalanced inputs to a system without internal system reconfiguration. The present invention thus also provides for a single-port test connection that allows signal monitoring whether the connected signal line is balanced or unbalanced. This invention further provides for the inclusion of an electronic test port controller that advantageously allows a user to electronically reroute any one of the system data inputs and outputs to a common port for monitoring or testing. This design saves panel space, reduces the possibility for operator error and equipment damage, and allows switching of a monitoring function between data lines without disturbing ongoing data communication.
The foregoing and other objects, features and advantages of the invention will become more readily apparent from the following detailed description of a preferred embodiment of the invention which proceeds with reference to the accompanying drawings.
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patent: 4300182 (1981-11-01), Schweitzer, III
patent: 4338647 (1982-07-01), Wilson et al.
patent: 4736403 (1988-04-01), McAlevey et al.
patent: 5228072 (1993-07-01), Ingalsbe et al.
patent: 5554038 (1996-09-01), Morlion et al.
patent: 5583440 (1996-12-01), Bisher
patent: 5681172 (1997-10-01), Moldenhauer
patent: 5886530 (1999-03-01), Fasnacht et al.
patent: 6381269 (2002-04-01), Gradl et al.
Armistead R. Ashby
Metcalf David W.
Zheng Danyang Raymond
Cisco Technology Inc.
Marger Johnson & McCollom
Oda Christine
Sundaram T. R.
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