[Discuss] Wire tester (like a tone tester)

[cra at WPI.EDU (Chuck Anderson)]

On Thu, Oct 02, 2014 at 09:28:06PM -0400, Bill Ricker wrote:
> Back in the days of 10BaseT coax runs with BNC T-couplers and
> terminators, I used a BNC-banana plugs adapter on a cheap VOMeter to
> check if visibility was to one terminator or two.  (50? if one,
> broken, or 25?=2 in parallel if properly configured.)
> 
> > Now, if any of the wiring between the wall and the patch panel is a
> > problem, is there similar testing gear to check on the wiring itself
> > (i.e Cat 6, PoE, etc) to help validate no kinks or broken wires?
> 
> A DC voltmeter with RJ-45 modular plug on a pigtail should let you
> check for PoE ?

No, power won't be applied unless the PSE (power-sourcing equipment)
detects a PD (powered device) at the far end.  A simple resistor
should allow that to happen though.  From
https://en.wikipedia.org/wiki/Power_over_Ethernet :

"PD indicates that it is standards-compliant by placing a 25 k?
resistor between the powered pairs. If the PSE detects a resistance
that is too high or too low (including a short circuit), no power is
applied. This protects devices that do not support PoE. An optional
"power class" feature allows the PD to indicate its power requirements
by changing the sense resistance at higher voltages. To stay powered,
the PD must continuously use 5?10 mA for at least 60 ms with no more
than 400 ms since last use or else it will be unpowered by the PSE."

> (shouldn't that properly be an RP-45?)

Actually, the correct designation is 8P8C Modular Plug.

> I do have a pocket-size jack-checker that indicates presence of data
> and if 10G or 100G if inserted into a dubious RJ45 ethernet jack. With
> a RJ45 double-jack adapter (sold as cable extender?) it would report
> if cable is passing data beyond the wall. 

Not sure what you are saying here.  A "double-jack adapter" sounds
like those splitters that plug into a jack which is connected to a 4
pair UTP cable and split it to two jacks, each with 2 pair.  You would
need two such adapters, one on each end of the single UTP cable run,
and it would only work for 10BASE-T or 100BASE-TX (10 Mbps and 100
Mbps Ethernet).  1000BASE-T (1 Gbps Ethernet) requires all 4 pairs.