Network Interface Cards and Modem

The most important devices in networking , with them there will be not networking world

• NIC - Is a printed circuit board (PBC) that allows communication to and from a computer to the out side world. NIC requires Interrupt Request (IRQ), Input/Output (I/O), memory space and driver to perform it functions. Today NIC is simply installed to the computer. The plug and play concept is used to installed NIC driver. You only need to slot the NIC to the computer expansion slot and run the driver software and wait for successful result of the installation.

• Modem - A device that enable the computer to communicate to the world via telephony line. At this point, the modem will connect your computer to the outside virtually via Public Switched Telephone Network (PSTN). The function of a modem is to convert digital signal to an analog signal before entering the PSTN, then convert the analog signal to digital signal when the signal reaches its destination. Converting from digital to analog is known as modulation and analog to digital signal is known as demodulation. There are two types of modem communication: the first type known as asynchronous and the second type is known as the synchronous. Asynchronous communication means that the entire signal will be sent including specified character with control bits which consists of start bits and stop bits. These bits will differentiate between the starting bits and the ending bits. Synchronous communication means that the data will be sent out in blocks of bytes. This blocks of bytes is analyzed, verified and acknowledged by the computer on the destination side and it is asked to accept or reject the blocks. If rejected, the blocks are requested to be resent.

Remember this:

Network Interface Cards
1. Design within PCB
2. Usually use the plug and play methods
3. needs Interrupt Request (IRQ), Input/Output (I/O), memory space and a driver

Modems
1. Connect the outside virtually via Public Switched Telephone Network (PSTN).
2. convert digital signal to an analog signal before entering the PSTN
3. convert the analog signal to digital signal when the signal reaches its destination.
4. two types of modem : asynchronous modem and synchronous modem.