In OSI Physical layer the following Network Equipment’s are involved.
- Network Interface Card
- Medium (Cables and Connectors)
Network Interface Cards:
NICs connect a computer to the Network. They can be integrated to the Motherboard or can be a separate Card (PCI,ISA etc).
A WIC (WAN Interface card) is used in WANs to connect a router to a Digital Circuit (Such as T-1). A WIC has built in CSU/DSU (Channel Service Unit/Data Service Unit).
Medium (Cables and Connectors):
There are varieties of Cables and Connectors used in Networking depending upon the type of Network and the distance of the Network segment. For detailed discussion, see http://karunsubramanian.com/security/network-cables-and-connector-types/
A device that amplifies the signal to reduce the effect of signal loss (attenuation)
A Hub (concentrator) is a device that connections multiple devices (Computers, printers etc) in a LAN (Local Area Network)
Passive Hub: Data enters one port and leaves all other ports with no amplification or modification of the data.
Active Hub: In addition to a functionality of a passive hub, an Active Hub amplifies the data (like a repeater). It is sometimes referred to as Multi Port Repeater
Note: A switch acts in Data Link Layer and is almost like a Hub except one major difference. A switch does not automatically send data to all the ports of a switch. Rather it sends the data ONLY to a designated port.