Types of Fax Machines
While older fax machines (before 1980’s) use to send the data in analog format, modern fax machines transmit the data in digital format. The resolution capabilities, data transmission rate and the printers also help us to classify the fax machines. There are also various ITU-T standards which also distinguish one fax machine from another.
Here is how fax machines are classified:
By Grouping
Group 1 and Group 2 fax machines are much slower than Group 3 and Group 4 fax devices. They send the data in analog format and follow T.2 and T.3 standards of ITU-T. Using a Group 1 fax, sending a single page may take up to 6 minutes while it is 2 minutes with a Group 2 fax machine. After digital fax machines became popular in late nineteen nineties, both Group 1 and Group 2 machines became outdated and currently, only Group 3 and Group 4 faxes are manufactured.
Group3 and Group 4 faxes use digital format and other sophisticated techniques like compression of data so the transmission is much faster than older fax machines.
A Group 3 machine will take just ten seconds to send a page and offer various resolutions (like ‘fine’ or ‘superfine’). A Group 4 fax is even much faster and can use digital ISDN line and can send data at the rate of 64 Kbits/s.
Depending on fax modems
There are different types of fax modems that are used in Fax Machines. They are:
Class 1 and Class 2 fax modems require to be connected a PC which controls them via software. Data compression and fax session are often done by the software in the computer. The upgraded version, Class 2.1 can perform the fax session much faster, when compared with Class 1 and Class 2 fax devices.
Class 3 devices can perform faxing independently without a computer.
Data transmission speed
Various ITU-T standards are used in fax machines. The modulation techniques along with ITU-T standards provide different data transmission speeds. For instance, V.34 ITU-T standard with QAM modulation method enables a data transmission rate of 28800 bits per second. Likewise, TCM modulation method enables V.17 ITU standard fax device to transmit data at the rate of up to 14400 bits per second.
Compression methods used by fax machines to compress data before transmission of data also determine the time that a fax machine takes to send a fax.
