Hub is connection device which joins in a network. Hubs classified as the layer 1 device and small, simple and inexpensive device. Hub does not read data passing through it and does not know the source and. destination points. It simply receives the data packets, amplify the electric signal and then retransmit data packets on the network. Three types of hubs are exist in the network.

• Passive hubs:

Passive hub receives data packet and retransmits them on the network without amplify the electrical signal.

• Active hubs:

Active hubs are also known as Repeaters. They receives the data packets amplify them and retransmit on the network. For amplification they need the electrical signal.

• Intelligent hubs:

Intelligent hubs includes remote management and basically used in the large scale companies where number of units can be placed one on the top of other as stack.

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Repeaters

Repeater is used to regenerate the analog as well as digital signals which are distorted by transmission loss. Analog repeaters only amplify the incoming signal where as digital repeaters reconstruct the signal. In Ethernet topology hub is used as repeaters that connect two segments on the network. Repeaters are capable of moving data packets between different network media. In OSI reference model, repeaters work on Physical layer only.