modem

MODEM

In the transmitting mode, the modem accepts digital data and converts it to analog signals for use in modulating a carrier signal. The modulated signal sent through the telephone wire to the modem at the receiving end. At the receiving end of the system, the carrier is demodulated and then limitated in to the corresponding digital data. Now the computer can receive & process the digital data. The modem can be operated in different modes. The following one the modes of operation.
(1) simplex mode: In this mode, a modem provides transmission in only one direction.
(2) Half duplex mode : In this mode data flow is possible in one direction at one time and in the opposite direction at a second time. Ie. Data flow is possible in both direction, but not simultaneously.
(3) Full duplex mode : It permits transmission in both directions at the same time or simultaneously.

The electronic transmission of a document at a distant place via telephone line is known as facsimile of FAX. The diagram shows, how the fax machine send a fax copy of a document and reception of the copy of the destination.

To send a Fax copy of a document. Two fax machines are required. One at the transmitting of sending end and the other at the recoving end. The machine at the sending end should be in the receiving mode.
Working : when the document is fed into the machine, the optical scanner scams the document and generate light-signal in accordance with data recorded on the document. The light signal’s will be detected by the sensors, creates electrical pulses corresponding to the reflections from the document. This will be a digital signal. The digital signal will be generated into analog and modulated by the modem at the sending end. The modulated signals will sent