Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Instruments and devices for fault testing
Reexamination Certificate
1999-11-12
2002-08-20
Le, N. (Department: 2858)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Instruments and devices for fault testing
C324S508000, C324S542000
Reexamination Certificate
active
06437580
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to devices for testing and tracing electrical circuits; and, it relates more specifically to devices for identifying and continuity-testing cables and cable networks.
2. Description of the Related Art
Coaxial cables and cable systems are essential to the function of telephone systems; cable television (CATV) systems; security systems; closed-circuit television (CCTV) systems; local and wide area computer networks (LANs and WANs); and, other multi-node, and multi-user systems. Tracing individual cables through such systems, and confirming their electrical continuity, often causes significant problems. Cables are often not identified with corresponding tags, labels or color-coding at both ends, so technicians installing or testing pre-wire systems, or removing, repairing or re-routing the cables of an existing system, have to sort through and test each cable individually. This commonly entails sorting through a number of upstream cable ends at a junction box or panel, and testing each against individual downstream termini where they connect to separate televisions, workstations, security sensors, or the like.
In tracing a coaxial cable from its downstream terminus back to the junction box, a technician normally secures a short circuit or low-resistance cable terminator to the downstream terminus of the desired cable and then, back at the junction box, connects a volt-ohm meter (VOM) to each upstream cable end, one-by-one. All cables but the correct one will produce a substantially infinite resistance reading, while the desired cable will show continuity. If the standard a 75-ohm terminator is used at the downstream terminus, a 75-ohm resistance reading on the meter confirms that no mid-cable short is present. Proceeding one-by-one through a great number of cable ends is a very tedious, laborious process. And, it is even more difficult and time-consuming if the technician desires to determine which of a multitude of downstream termini is associated with a particular upstream end at the junction box. In that case, the technician must either affix a terminator to the upstream end and walk room-to-room or workstation-to-workstation connecting a VOM to each downstream terminus, searching for continuity. Or, the technician must connect the VOM to the upstream end of the desired cable at the junction box and, repeatedly, walk to a downstream terminus; connect a terminator; and, walk back to the junction box to read the meter.
Various devices have been used and proposed for more convenient testing and tracing in coaxial cable systems. Miniaturized, limited-purpose versions of VOMs having cables, probes, clips, adaptors, LED's, tone generators and streamlined cases are commonly available, but they are generally difficult to use among tangled masses of cable ends, and more often suited to toolbox rather than pocket transport. Even the smaller, simpler versions have significant drawbacks. For example, U.S. Pat. No. 4,864,225 issued to Long, et al. shows a cylindrical, battery-operated cable tester with a cable coupling on one end for axial, threaded engagement with a cable end, further including a continuity-indicating LED at the end opposite the cable coupling. A conventional cable terminator, for placement on a tested cable's opposite end, stores removably on the device's cable coupling. Although the Long, et al. device may be more convenient than meter reading, it would still have drawbacks in that it would be difficult to fit into tight places and to engage its threaded, axial coupling to cable ends. Furthermore, the device's LED is poorly positioned; it is set in a recess at the farthest point possible from the coupling end, which would make it least useful in checking for continuity during the process of engaging the coupling.
Accordingly, it appears there exists a need for an easily manipulable, easy to read device for testing and tracing cables in coaxial cable systems.
SUMMARY OF THE INVENTION
The cable continuity tester and tracer of the present invention is adapted to overcome the above-noted shortcomings and to fulfill the stated needs. It comprises: a body portion having proximal and distal ends; a portable power supply within the body portion; a connector at the body portion's proximal end having first and second contacts; means closely adjacent to the connector for visibly confirming continuity in a circuit; means for establishing a circuit from the first contact, to the power supply, to the visible circuit continuity-confirming means, through the body portion, and to the second contact; means selectively storable in secure engagement with the body portion for audibly confirming continuity in a circuit.
It is an object of the present invention to provide a cable circuit tester and tracer which has a built-in power source, and fits as easily in a shirt pocket as a pen.
It is a further object of the present invention to provide a cable circuit tester which includes a visible continuity indicator placed closely adjacent to the connector to which the cable under test is being coupled.
Yet another object of this invention is to provide a cable circuit tester which is both sized and configured to work in tight spaces.
Yet a further object of the present invention is to provide a cable continuity tester and tracer having a detachable toner unit able to be either press-engaged or threaded into a cable coupling.
Yet a further object of the invention is to provide a cable continuity tester and tracer with circuitry able to discern whether a line is shorted, or fitted with a low-resistance terminator cap.
Still a further object of the present invention is to provide a continuity tester and tracer able to detect both 50 ohm and 75 ohm terminator caps on tested cable lines.
Another object of the present invention is to provide a cable continuity testing and tracing kit, including adaptors for testing telephone lines, computer network lines and other types of cables and cable systems.
Still further objects of the inventive device disclosed herein will be apparent from the drawings and following detailed description thereof.
REFERENCES:
patent: 3979193 (1976-09-01), Hayes
patent: 4670709 (1987-06-01), Iredale
patent: 4740745 (1988-04-01), Sainz
patent: 4839599 (1989-06-01), Fischer
patent: 5285163 (1994-02-01), Liotta
patent: 5612616 (1997-03-01), Earle
Bernheim William S.
Nguyen Vincent Q.
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