What is a Modem, Repeater & Hub?

MODEM – MOdulator/DEModulator
MODEM is a network device which converts a computer’s digital signals to an analog transmission signal to use with telephone lines or cable TV lines or satellite connections and vice-versa.
MODEMS are necessary because public telephone lines, cable lines, and microwave media use electromagnetic waves, but computers use electric pulses.
Modems are used when more than one communication is to occur in the same medium. Modems can be selected to use different electromagnetic frequency bands.
Some of the different types of Modems are Dial-up Modems, DSL modems, cellular modems, Broadband Modems etc..

Repeaters are also known as signal boosters, signal amplifiers, Range extenders or signal regenerator.
Repeaters receive the inbound electrical, optical or wireless signals and retransmit the signals.
One type of repeaters amplifies all incoming electromagnetic waves, including undesirable noise. It is called as amplifiers.
Another type, known as signal regenerating repeater, strips data out of the transmission signal. Then reconstructs and re-transmits the signal on the other media segment.The new signal is boosted and exactly duplicated by this type of repeater.
Simply, repeaters are used to transmit the signal to the required distance beyond the capability of the transmission medium to some extent.
WiFi extender is a type of repeater.

Hub is nothing but a multiport repeater. Also referred to the concentrator.
Cables from network devices can be connected to the ports of the hub.
Hubs receive transmissions from connected devices and transmit the signals to the other connected devices.
Hubs are 2 types, Active and passive hubs.
An active hub regenerates or amplifies the received signals. Most active hubs are multiport repeaters.
A passive just connects medium segments together, does not regenerate or amplify signals.

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