
Devices work as advertised, they split the ethernet port into two separate cables as four wires are not typically used for 100 megabit connections. If you need a gigabit connection, you're out of luck as it uses all eight wires. In that case, you'd be better off getting two inexpensive managed switches that support VLANs and configuring them to isolate your networks.

TP-Link Archer T4U Plus AC1300 USB 3.0 WiFi Network Adapter
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π Juiced Systems Silver BizHUB USB-C Multiport Gigabit HDMI Hub with 3 USB 3.0 Ports, Gigabit Ethernet, 4K HDMI, SD/Micro SD, and USB-C Power Delivery
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π uni USB C Hub with Ethernet Adapter, 4K HDMI, Gigabit Ethernet, and 3 USB 3.0 Ports for MacBook Pro, iPad Pro, XPS
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π USR-TCP232-410s: RS232/RS485 Serial to Ethernet Adapter/IP Device Server with DHCP/DNS Support
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