black box LB308A 
型号： LB308A 
产品描述:10BASE-T/100BASE-TX Hardened Ethernet Extender Switch, 8-Port
Further Details
Supports IP multicast filtering through IGMP snooping.
with NEMA TS1 and TS2 environmental requirements for traffic
equipment.
Supports port-based VLAN and IEEE 802.1q VLAN  and GVRP.
Up to 24 static secure MAC addresses per port.
Fanless design means fewer maintenance hassles.
DIN rail mounting kit included.

Hot swap extender without powering down.
A switch configures the extender for local (CO) or remote (CP) use.

This 10BASE-T/100BASE-TX Hardened Ethernet Extender uses  to provide
 an easy, inexpensive way to extend the reach of your Ethernet network 
over ordinary voice-grade copper wire. Use the Hardened Extender for
harsh environments and extended temperature ranges. Because you use your
existing copper infrastructure, you  on cabling costs. Plus it has an
internal switch and eight Ethernet ports, so you can use it to easily add
remote ports at the edge of your network.