Cable continuity checkers were the first dedicated LAN cabling testers when networks migrated from coaxial to twisted pair in the late 1980s . These early testers became known as ‘ blink boxes ’ - a nickname that is still in use today . LEDs ( light emitting diodes ) display the test result and regardless of brand or model it is universal that four green LEDs = PASS . LEDs were used because they were inexpensive and made it possible to put a cable tester into the hand of every installer . While LCD ( liquid crystal display ) technology was not expensive in high volume production , cable checkers were low volume products so developing custom LCDs was cost prohibitive . As technology advanced , custom LCD panels reached price points enabling LCD cable verifiers to be offered at affordable prices . With intuitive graphics , LCD verifiers allow installers to quickly repair complex cabling faults that are difficult to display on an LED verifier .
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Choosing between a blink box and an LCD verifier
To display faults , LED verifiers have troubleshooting modes where fault LEDs ( open , short , reverse , split ) blink in conjunction with the LED that corresponds to a pair in the cable . The tester scans each pair while the user ‘ decodes ’ the sequence of blinking LEDs to identify the cabling fault – hence the name ‘ blink boxes ’.
Blink boxes only communicate wire map status to the user . Although information that falls outside of common faults and pair number is difficult to display with LEDs , they do have advantages . Above all , it is very easy to see four green LEDs in any lighting condition compared to ‘ reading ’ the result on an LCD . For this reason , blink boxes remain popular today and are the go-to tester for many installers despite their limitations .
The ability to display more than just wire map data makes LCD verifiers the best choice for the majority of installers . LCD verifiers can display cable length , distance to open / short , connection speed on live networks , analog vs . digital phone service ,
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‘ A common problem faced by users of simple cable verifiers is tracing a live network cable from the work area back to the network switch .’ |
PoE status , etc . Arguably , the single feature of LCD verifiers that improves productivity most is support for multiple remotes . Using multiple , inexpensive , numbered remotes , a single installer can connect to more than a dozen cables at once and test each one from the patch panel in seconds without having to walk back and forth each time . LCD verifiers display the test result along with the ID number of the remote , reducing singleperson testing of a job site to a fraction of what it would be with an LED verifier .
Using a cable verifier for network and PoE detection
Advanced features like network and PoE ( Power over Ethernet ) detection have been the most sought after features in cable verifiers . With so much integration , virtually every communication system in residential and commercial installations uses twisted pair ‘ category ’ cable and technicians often find themselves working on jobs with both active and inactive cabling . Products like the Ideal Networks VDV II Pro bridge the
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February 2017 | 35 |