Types of Modem

Internal computer modems:

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An internal modem is a device installed inside a desktop or laptop computer, allowing the computer to communicate over a network with other connected computers. There are two types of internal modems:

dial-up and WiFi® (wireless). The former operates over a telephone line and requires a network access phone number and logon credentials to make a connection. The latter can connect wirelessly and without credentials in certain cases. The non-qualified term “internal modem” commonly refers to the dial-up modem, as technologies that followed are used with qualifiers to differentiate them.

Some computers have an internal modem which can be a built-in modem or a PC card modem.  Internal computer modems are used with Dial-Up Internet connection through a couple of RJ-11 connection. Also called copper telephone lines, the RJ-11 allows computer to receive and send data Internal computer modems are usually 56K modems which mean that the modem is able to receive 56 Kbps (56 kilobits or 56000 bits per second) of data. This kind of data transmission is called downstream transmission, came from a provider and transmitted over telephone lines. Commonly it is the standard bandwidth with telephones lines.

However because Internet is a two-way system, data must also flow from the client to the (server) provider. For this purpose the computer can use 56K modems V90 to flow back 33.6 Kbits/s of upstream transmission rate. On the other hand the 56K modems V 92 is able to provide 48 Kbits/s of upstream transmission rate.

External modems.

An External modem can be used to the same purpose and in the same conditions as internal computer modem. However external modem is a small box that uses other kind of interfaces to be connected to the computer. It could be a serial modem, named thus because it uses the serial port to connect to the computer. Usually installed on the back of the computer, the serial port is an easy-to-install option for the external modem. The same small box, on the other hand, can be an USB modem which normally uses USB port usually placed on the back or in front of the computer.

First of all external modem can be a Dial-Up modem but more expensive than the internal.

Another type of external modem that may consider two important types of modem: cable modem and DSL modem. All ISPs usually supply a specialized modem named digital modem in the broadband package.

It’s important to notice that cablemodem has to connect to an Ethernet card, placed on the computer PCI slot to provide a broadband internet connection to the user.

Cable modem:

cable modem.jpg

A type of modem that allows people to access the Internet via their cable television service.

The cable modem uses a coaxial cable television lines to provide a greater bandwidth than the dial-up comuter modem. An extremely fast access to the Web is providing by the cable modem with downstream transmission up to 38 Mbits/s and an upstream transmission up to 1 Mbits/s.

Data can be transferred over cable lines much more quickly than over traditional phone lines. Transmission rates are typically around 1.5 megabits per second. Faster transmission is actually possible, but speed is usually restricted by the cable company's (typically slower) connection to the Internet.

Unfortunately this transmission rate fluctuates with the number of users because of the shared bandwidth on which the cable technology is based.

DSL modem:

dsl modem.jpg

DSL (Digital Subscriber Line) modem is exclusively used for connections from a telephone switching office to the user.  DSL modem is a device used to connect a single computer or router to a DSL phone line, in order to use an ADSL service. Like other modems it is a type of transceiver. It is also called a DSL Transceiver or ATU-R. The acronym NTBBA (network termination broad band adapter, network termination broadband access) is also common in some countries. Some of the ADSL modems also manage the connection and sharing of the ADSL service with a group of machines: in this case, the unit is termed a DSL router or residential gateway

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