Modems

What you need to look for

A modem is a device that modulates outgoing digital signals from a computer or other digital device to analog signals for a conventional copper twisted pair telephone line and demodulates the incoming analog signal and converts it to a digital signal for the digital device.

In recent years, the 2400 bits per second modem that could carry e-mail has become obsolete. Nowadays, most new personal computers come with 56 Kbps modems. With Digital Subscriber Line (Digital Subscriber Line) systems now being deployed in a number of communities, bandwidth on twisted-pair are in the megabit range. This article dicusses the features to take into consideration while selecting a modem.

Speed
Virtually all new modems conform to the V.90 56Kbps standard, but you may or may not be able to actually get a 56Kbps connection from your office or home. V.90 modems require very clean phone lines. However, they won't work on phone lines that pass through a digital line concentrator ( equipment commonly used to combine many phone lines into a single cable). Before you spend the money to upgrade your modem to 56Kbps, check to see if your line is 56Kbps capable. Else, you'll be limited to V.34 (33.6Kbps) connection speeds.

Internal modems
If you're shopping for an internal modem, you'll have to choose between ISA bus and PCI bus. ISA is a standard bus (computer interconnection) architecture that is associated with the IBM AT motherboard. It allows 16 bits at a time to flow between the motherboard circuitry and an expansion slot card and its associated device(s).

PCI or Peripheral Component Interconnect is an interconnection system between a microprocessor and attached devices in which expansion slot are spaced closely for high speed operation. Using PCI, a computer can support both new PCI cards while continuing to support Industry Standard Architecture (ISA) expansion cards, currently the most common kind of expansion card. PCI is now installed on most new desktop computers, not only those based on Intel's Pentium processor but also those based on the PowerPC

Some ISA cards and most PCI cards are internal modems, often called Winmodems. You may want a PCI modem if you have other ISA cards such as sound cards that take up system resources. ISA cards are also more prone to IRQ incompatibility during installation. The IRQ (interrupt request) value is an assigned location where the computer can expect a particular device to interrupt it when the device sends the computer signals about its operation.

These modems use a simplified design that reduces the cost of the modem card by placing much of the burden of the modem's operation (usually done by an onboard modem controller chip) onto the host PC's CPU. If you have a fast PC, you may never notice the difference. Users of 266MHz or slower PCs may experience system slowdowns, especially when playing multimedia or sound clips while the modem is active. Hard-core multiplayer gamers should avoid controllerless modems at all costs.

If you use an operating system other than Windows 95 or 98, be sure that the modem vendor provides drivers for your OS. Most internal modems don't work with Windows NT or Linux.

Telephony Features
Some modems provide a telephone interface feature that lets you use the modem—along with your PC's microphone and speaker—as a speakerphone. However, only a few provide the clarity you get from a conventional phone. You also require a special computer headset, which will cost you extra for privacy.

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