On my Cyber Power 825 AVR UPS it has two ethernet connections: one labeled in and the other labeled out. What's the difference?
1 Answer
Most UPS will come with said Ethernet jacks, which protects you from power surges coming from your networking device (UPS also act as surge protectors).
However, it's unlikely that your networking devices would randomly generate these abnormal amount of current down the wire; instead, it's more to protect you from adverse weather conditions, i.e. your house getting struck by lightning. Dangerous amounts of current could pass through the telephone wire and fry every device in its path. This is where the Ethernet jacks come in handy. Not only that you're protecting your PC through its mains, but you're also protecting yourself from the LAN side.
For the two Ethernet ports, the one labeled IN is used to connect the UPS to the router/switch; OUT then goes to the computer.