How to choose a modem

How to choose a Modem

Telephone Modems | Cable Modems | DSL Modems | ISDN Modems

What is a Modem?

When you connect to the Internet, you might connect through a regular computer modem, through a local area network connection in your office, through a cable computer modem or through a digital subscriber line (DSL) connection. If you want to send a fax from the computer , you also need a modem. Wireless computers use wireless modems.

Telephone Modems: The word "modem" is a contraction of the words modulator and demodulator. Usually modem includes sending and receiving modems. The sending modem modulates the data into a signal that is compatible with the phone line, and the receiving modem demodulates the signal back into digital data.

Design

Internal modems: These modems go inside the computer, and usually plug directly into the motherboard.

External modems: These modems are embedded in a separate box that sit outside the computer, and usually plug in through a serial port, or a USB port. External modems cost the most, but have the benefits of being easily installed. Often they have the indicators that tell you the status of your connection.

Modem features

Modem speed: Modem speed is rated in bps (bits per second). So a 56k modem transmits at 56,000 bits per second in theory. While 8 bits make a byte, and 1024 bits equal one kilobits, a 56k modem will transmit a maximum of approximately 7 kilobytes of information every second.   A modem will never connect higher than what it is rated for. For 2 connected modems, for example a 28.8k modem and 56k modem, the latter can not connect at higher than 28.8k speeds. When an end user looks at his connection speed, he may see one of two things: either the speed that his modem is talking to the other modem or the speed his computer is talking to his modem. Modems generally come in the following speeds: 2400, 9600, 14.4k, 28.8k, 33.6k, and 56k.

Protocols is a language and syntax that enables computers to speak to one another. Different modems use different protocols:

V.34 - for 28.8k and 33.6k communications.

K56Flex - for 56k communication, created by Lucent and Rockwell.

X2 - for 56k communication, created by US Robotics (3com).

V.90 - This is the International Standard for 56k modems.

V.92 - This is an ITU (International Telecommunication Union) standard for 56K modems, but three new features have been added -- faster connections (on 50%), better uploading, and data and voice support:

NOTE: the V.92 features will not be immediately available with many ISPs, because it requires upgrades at their end - so don't rush out and buy a V.92 modem until you know your ISP has installed it.

There are 2 protocols that are used to correct errors on a connection:

V.42 (LAPM) – This is the International Standard for doing Error Correction

MNP – an old protocol that most modems support.

    Compression helps to speed up transmission of information. There are 2 protocols for compression:

V.42bis – This is the International Standard for Compression. It only works with V.42 Error Correction

MNP5 – This is an older protocol that most modems support. This only works with MNP Error Correction.

Modem drives (software). Drivers will usually be provided with the modem or the computer. For name brand modems, the drivers normally can be found on the manufacturers web site.

Cable Modems make access to TV cable, and let you get high-speed internet access. Availability is still limited in many areas, but is growing rapidly.

DSL Modems: DSL (Digital Subscriber Line) service is usually offered through the phone the company/ISP. Most major cities have some neighborhoods where DSL is available. There is no need to "dial up" when using DSL because as long as the computer is turned on, there is connection to the Internet. This standard usually produces speeds of 1 - 1.5 Mbps downstream and 128 - 512kbps upstream.

Here are the Pros and Cons of DSL

Pros	Cons
You can leave your Internet connection open and still use the phone line for voice calls	The service is not available everywhere
The speed is much higher than a regular modem (up to 1.5 Mbps )	A DSL connection works better when you are closer to the provider's central office
DSL doesn't necessarily require new wiring; it can use the phone line you already have	The connection is faster for receiving data than it is for sending data over the Internet
The company that offers DSL will usually provide the modem as part of the installation

There are many types of DSL now.

One of the more popular versions of DSL is the "Lite" version, or G.Lite.

Very high bit-rate DSL (VDSL) - This is a fast connection, but works only over a short distance.

Symmetric DSL (SDSL) - This connection, used mainly by small businesses, doesn't allow you to use the phone at the same time, but the speed of receiving and sending data is the same.

Rate-adaptive DSL (RADSL) - This is a variation of ADSL, but the modem can adjust the speed of the connection depending on the length and quality of the line.

ISDN Modems: ISDN is an abbreviation for Integrated Services Digital Network. This type of network is digital from end to end. The POTS (Plain Old Telephone System) is mostly digital, except that it is s still analog from your home to the switch, digital from there all the rest of the way through to the destination (we're assuming for the internet world mainly because most good ISP's are digital now all the way ). The basic rate line is an ISDN user-to-network interface made up of three communications channels-two B channels for voice, data, etc. and one D channel for signaling, call setup (dialing) etc. ISDN most often uses existing copper wires, your home or office may not need to be rewired, but you will need a new wall jack. Advantages of ISDN over conventional analog lines:

there is no such thing as a noisy or fuzzy line.
always runs at 64kbps
ability to bond multiple "B" channels to get speeds of 128kbps
call Setup is very fast (dialing, handshake and authentication), usually under 2 seconds (compared with 15 seconds at least for most analog modems)
ability to get 2 calls at the same phone number (one line is for voice, and the other line for your internet connection)

Wireless Modems convert digital data into radio signals and back. Wireless modems work in conjunction with the computers to transmit data. They connect directly to any standard PC Card slot and support a maximum data transmission rate of 19.2Kbps (kilobits per second). You should choose carefully a wireless modem if you need to access graphics, audio files, or extensive amounts of text data. Wireless modems can be used up to 20-30 miles (30-50 KM). Operation is in the 900 MHz and 2.4 GHz. Modem names include - BreeseLINK, LATNET-Radio Data Links, AirLink Wireless Modems, Open Minds, etc.

Comparison-shopping Center: You can use directly the Comparison-shopping Center to buy on the Internet a product with the lowest price.

Pay Attention to NexTag Trusted Seller Program. Sellers qualify as NexTag Trusted Seller by being listed on NexTag.com for at least 6 months and by meeting the following criteria:

Receive positive customer ratings and reviews

Supply correct store information including a contact phone number

Provide correct product information including price, shipping, and availability

Identify product conditions correctly (New, Like New, Refurbished, etc?)

Honor prices and policies displayed on their website

Address customer service complaints quickly and fairly

Welcome▼