Fax / Copier Combination Machines

What a fax / copier combination machine is

A fax / copier combination machine is a single device that can both send and receive facsimiles and make local photocopies. The category exists because a fax terminal already contains the two subsystems a copier needs: a scanner to digitise an outgoing page and a printer to render an incoming one. Adding a copy function is largely a matter of routing a freshly scanned page to the built-in print engine instead of encoding it for the telephone line. Because the class is defined by this combination of functions rather than by one product, its capabilities are best described at the level of the standards these machines share.

Why faxing and copying combine so naturally

Sending a fax and making a copy follow almost the same internal path. In both cases the machine scans the original into a line-by-line image; the only difference is the destination. A fax hands that image to a modem, which negotiates with a distant machine and transmits it over a phone connection, whereas a copy sends the same image directly to the local printer. Reusing one scanner, one image path, and one printer for both jobs is what lets a combination machine offer copying at little extra cost, and it is the same insight that later produced multifunction office equipment.

The Group 3 standard these machines implement

Most fax / copier combination machines are Group 3 fax terminals. Group 3 is defined by the ITU-T (formerly CCITT) telecommunication standards, principally Recommendation T.4, which standardises the terminal, its page coding, and its resolutions, and Recommendation T.30, which specifies the call-establishment and negotiation procedures a machine follows over the general switched telephone network. Standardisation at this level is what allows machines from different manufacturers to interoperate, and it is why a combination machine's fax behaviour can be described accurately without reference to any single brand. Under T.4, a standard-resolution page is scanned at roughly 203–204 dots per inch horizontally by 98 lines per inch vertically, and a fine-resolution page doubles the vertical detail to about 196 lines per inch. Group 3 pages are compressed with the Modified Huffman (MH) one-dimensional or Modified READ (MR) two-dimensional schemes of T.4, with the more efficient Modified Modified READ (MMR) coding defined in Recommendation T.6.

Modem speeds and Super G3

How quickly a Group 3 machine sends a page depends on the modem modulation it negotiates under T.30. Standard Group 3 machines use the ITU-T V.27ter (2,400 and 4,800 bit/s), V.29 (7,200 and 9,600 bit/s), and V.17 (up to 14,400 bit/s) modulations. Later "Super G3" machines adopted V.34 signalling, which raises the ceiling to about 33,600 bit/s. Higher throughput mainly shortens transmission time; it does not change the reconstructed image's resolution, which is fixed by the scan mode.

Marking technologies: from thermal paper to plain paper

Combination machines have used the same succession of printing technologies as fax machines generally. Early Group 3 machines printed with direct thermal heads onto heat-sensitive rolls, which was inexpensive but produced output on curling, fading thermal paper. From the mid-1990s the market moved to "plain-paper" faxing, in which the received or copied image is rendered by a thermal-transfer, inkjet, or laser print engine onto ordinary cut sheets. The choice of engine largely determines a combination machine's copy quality, running costs, and whether its output is archival.

From combination machine to multifunction device

The fax / copier combination is a step on the way to the multifunction device, also called an all-in-one or MFP. Once a machine contained a scanner, a print engine, and a controller, manufacturers exposed those subsystems as separate features, adding computer printing and scan-to-file to the existing copy and fax functions. The result is the familiar office device that prints, scans, copies, and faxes from one chassis. Standalone fax / copier units have largely given way to these multifunction machines, even as the underlying Group 3 fax standard they implement has remained stable.

Reference scope

This page describes a class of device and sources its technical claims to the ITU-T standards that define Group 3 facsimile and to encyclopedic references, rather than to any one product. Figures such as resolutions and modem speeds are those specified by the relevant Recommendations; specifications that vary by model — dimensions, memory, pages-per-minute copy speed, or price — are deliberately omitted because they cannot be stated for the class as a whole. It is not a buying guide and quotes no current pricing or availability.