Question

What is FAX machine? Draw it's block diagram and explain it's working.

Answer 1

FAX machin: The FAX is the symbol for facsimile which means exact copy of writing, picture etc. FAX is indeed the electronic transmission and reproduction of a document as such in same form at a distant place. Shows the block diagram of FAX machines for sending a document from one place to the other.
Construction and working:
The main parts of a Fax machine are:
(i) Optical scanner,
(ii) Photo sensor,
(iii) Modem and
(iv) Printer.
(i) Optical Scanner: It scans the document to be transmitted in form of white and black spots. Light from a strong source is made incident on the document. The part of the document where there is ink, reflected a very small amount of light, while the part where there is no ink, reflects a large amount of light. Generally the document is kept stationary and the scanning is done by moving the source of light. Thus we get a light signal of the document.
(ii) Photo sensor: It changes the light signal into the digital signal.
(iii) Modem: In the transmitter, the modem changes the digital signal into the analog signal, while in the receiver the modem changes the analog signal into digital signal again.
(iv) Printer: It creates the photocopy of digital signal in the receiver. Thus is start with the sender dials the phone number of the Fax machine at the receiving end is set as the receiver. Then the document to be transmitted is fed into the Fax machine. The optical scanner scans the document and changes it to a light signal. The photo sensor then changes the light signal into the digital signal creating a high voltage pulse at more intensity of light and a low voltage pulse at less intensity of light. Then the modem inside the transmitting Fax machine converts the digital signal to the analog signal which are transmitted to the receiving Fax machine through the telescope line. At the receiving end, the modem in the Fax machine converts the analog signal back into the digital signal which is then printed by the printer in form of white and black spots to reproduce an exact copy of the original document.