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Appendix 3 - Considerations Regarding Cables and Grounding:
This appendix discusses types of Ethernet cable that should be used with the EA-1 device.
Ophir supplies a short “cross-over” cable along with the EA-1 device, which can be used for initial setup if required. A
“cross-over” cable is one where the Transmit pins on one side are shorted to the Receive pins on the other side, so
the signals “cross-over” with each other. Unlike the EA-1, most Ethernet devices available today (switches, network
cards, etc.) are capable of automatically detecting when they need to switch over their signals between Transmit and
Receive, and therefore they can work with either a cross-over cable or a regular “straight-through” cable where the
pins are connected one-to-one from one end of the cable to the other. Therefore in most cases, the EA-1 can be
connected to any Ethernet device or switch using any type of cable whether it is cross-over or not cross-over. The
cross-over cable is supplied to cover those rare cases where this is not the case.
Other considerations regarding the cable are whether to use shielded or unshielded cable; and whether to use “non-
isolated” cable where the ground shield is shorted all the way through from one end to the other, or isolated cable
where the ground is not shorted all the way through. These considerations need to be taken according to the
particular network and equipment being used, and in most cases it does not affect the operation of the EA-1 device.
One further consideration that may be important for some customers: versions of the EA-1 manufactured up to
~June 2018 do not have a short between the local ground (connected to the metal box) and between the Ethernet
ground (connected to the metal part of the RJ45 connector). Units manufactured after ~June 2018 meet full
requirements for ESD and EMC compliance. These units do have a short between these grounds and therefore will
no longer be “isolated”. If isolation is important to the customer, when using units manufactured from ~June 2018
and later, it will be necessary to use an “isolated” cable where the ground shield is not connected all the way
through from one end to the other. Whether or not isolation is important will depend on the specific setup of the
equipment, and on whether or not the sensor attached to the EA-1 is itself isolated from the surrounding
equipment.