Question

List of types of modems ?

Answer 1

Types of Modems

Standard Modems

Most standard modems today are either internal or external.
An internal modem is used inside of the computer and connects directly to the I/O BUS. The internal modem does not require a separate power supply as it gets it's power from the computer's internal BUS nor does an internal modem require a serial port or connecting cables to that port. An internal modem will contain a 16550A UART or equivalent circuitry, which will aid in fast data throughput to the computer. Internal modems are usually cheaper than external modems as well. Internal modems are a little more difficult to install than external modems and an available ISA slot must be present to install it into the computer.
On an external modem it is helpful that the modem be connected to a 16550A UART serial port to be assured of the maximum data throughput and of course, an available serial port is necessary. An external modem connects to a serial port on the PC or TI and requires the use of a connecting cable between the PC (or TI) and modem, a power connection and of course a place to put the modem itself. The advantage of an external modem is that external modems can be easily moved from one computer to another and the lights on the modem itself can aid in the diagnosis of any problems. Furthermore, an external modem can easily be reset by turning it off whereas an internal modem can not just be turned off without turning off the system.
Back to top.
Fax Modems

These allow you to send and receive faxes. The fax part of the modem sends/receives data that is interpreted as a picture. One can create documents on a computer (resumes, papers, thesis proposals) and send them direclty from the application to a fax machine or a computer with a fax modem. Instead of sending the print job to the printer you're sending it to the fax modem. The information is sent over telephone lines to a remote fax machine or fax modem. That is, any file in your computer can be sent to a fax machine or another computer with a fax modem. One can fax résumés, thesis proposals, etc. to a fax machine in a matter of minutes.
Back to top.
Intelligent Modems
Intelligent modems are more expensive modems that contain internal read only memory (ROM) coding and microprocessor chips to provide sophisticated communications protocols and diagnostic checking within the modem itself. Some of these intelligent modems not only perform digital-to-analog conversation but also operate as multiplexers, security restrictor devices, encryption devices, error detection and retransmission devices.
Back to top.
Short Haul Modems
Short Haul modems provide transmission of data at medium to high rate in either direction (full duplex). They are also used in the control of remote devices in their network. In a short haul modem, you use your own wire pair cable to transmit direct electrical signals. This type of modem is also called line driver. This device consists of a box approximately the size of a cigarette pack. Because short haul modems do not require an external power source, getting their power through the serial port, they sometimes are referred as modem eliminators. These modems are generally used in business and not the private user. The farther the signal has to travel; the amount of data is reduced. Generally short hauls are synchronous, full duplex.
For Example:
Telebyte M 431: V.35 Interface, full duplex on single twisted pair, up to 128 Kbps, built-in diagnostics, bi-directional handshake, 9600 bps at 3.6 miles, and cost: $575.
CIM M 74: V.35 Interface, full duplex on two twisted pair, up to 19.2 Kbps, bi-directional handshake, .6 Kbps at 10 miles, and cost: $155.
Back to top.
Wireless Modems
Wireless modems transmit the data signals through the air instead of by using a cable. They sometimes are called radio frequency modem. This type of modem is designed to work with cellular technology, and wireless local area networks. Wireless modems use two types of transmission to tr

Answer 2

A Modem is a small box which connects one's devices to the Internet by using cables. A modem acts like a digital translator which takes an information signal from the cable, fibre or phone lines and makes it available to the computer.

The three types of modems are Cable, Digital Subscriber Line ((DSL)) and Dial-up.

• A Cable Modem wields coaxial cables which connect to the back of the modem and the bolt-like portal in the wall or on the cable box. This type of modem is preferable as it delivers high-speed internet to the devices.

• DSL and Dial-up Modems use a cable which connects to the phone line. DSL, though, still allows one to use their landline telephone while it is connected to the internet.

#SPJ2