Physical Layer/Devices

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The physical layer is the lowest layer. This layer provides mechanical, electrical and other functional aids available to enable or disable, they maintain and transmit bits about physical connections.

Hubs

are devices commonly used to connect segments of a LAN.

It contains multiple input/output ports

when signal is at any input port, this signal will be made at all output ports except the one it is coming from.

Cables

In Wired network architecture (e.g Ethernet)

cables are used to interconnect the devices.

some of the types of cables are coaxial cable,

optical fiber

twisted pair cable

Twisted Pair Cabling and Duplexing

The most common type of cabling used for connecting computing devices is known as twisted-pair

It's called a twisted pair cable because it features pairs of copper wires that are twisted together.

These pairs act as a single conduit for information, and their twisted nature helps protect against electromagnetic interference and crosstalk from neighboring pairs.

Duplex communication is the concept that information can flow in both directions across the cable.

Repeater

transmission systems

regenerate analog or digital signals distorted by transmission loss

Analog repeaters can only amplify the signal whereas a digital repeaters can reproduce a signal to near its original quality.

Modem

Modem stands for MOdulator/DEModulator

converts digital signals generated by the computer into analog signals

cable line and transforms incoming analog signals into digital equivalents