60.6.3 Facsimile gateways

The transmission of facsimile documents and of electronic mail or computer generated text are usually kept separate. However the wide population of G3 machines has encouraged users on electronic mail or local area networks to request interoperation. This is usually achieved by fitting a gateway on the computer network to convert the information to the T.4 and T.30 facsimile format for onward transmission.

The problem is for incoming documents in the facsimile domain. These are virtually impossible to convert to the text environment and require onward transmission in a graphics mode with the high bandwidth and large storage capacity associated with raw image data. These facsimile documents are most conveniently printed out on a local facsimile unit and kept separate from the data system.

60.6.4 Pc fax cards

The widespread availability of G3 machines and the expansion card provision in desktop personal computers, has encouraged the devel­opment of specialised fax cards. With the addition of a dedicated PSTN interface card and support software, it is possible to make facsimile transmissions directly from PC memory without the image being printed. The performance depends on the balance between PC software capability, for example speed of compression, and the processing and memory capability of the card itself.

User expectations that the simple operation of fax machines be available in PC fax are beginning to be met together with back­ground operation of the PC in fax mode. However there are similar incoming document problem as for gateways:

1. Difficult to provide adequate soft copy memory.

2. Slow to print received pages.

3. Limitations of screen resolution or of whole page display.

4. Time to decode/display compressed image limits search mode.

One of the benefits of PC fax cards or fax gateways is their ability to send the equivalent of personalised mailshots by facsimile, a feature not normally available in the broadcast mode of facsimile transceivers which send identical documents to all destinations.

The fax modem fitted to these cards can also be used for PC to PC communication for file transfer over the PSTN. If the growth in this requirement continues, then discussions in CCITT are likely to provide an additional option within the G3 fax recommendations.

The convenience of communicating by facsimile can be extended to operation with the computer in the briefcase. Transmission di­rectly from the keyboard (actually from memory) and soft copy reception without printing are easily possible with existing fax standards over the PSTN.

Customer requirements dominate facsimile developments and the increase in use of the G3 interface in non-fax products is expected to continue although the replacement of documents in the briefcase by facsimile files in the laptop/notebook PC seems remote.

60.7 Facsimile futures

The PSTN remains the major communication network for the fore­seeable future with increasing opportunities on the ISDN. Facsimile terminals G3, G3-64kbit/s and G4 will continue to operate on these networks.

Facsimile transmission is particularly appropriate for the future because of the large compatible equipment base and because of the vast and continuing information base on paper and film.

Documents are required on paper for convenience, for availability (even in power failure) and for use when out of communication away from the office.

Development continues in CCITT with higher speed, higher res­olution transmission and with high speed character and mixed mode functions.

The potential for communication with this ubiquitous terminal is hardly touched. Interfaces into the facsimile domain to use the proven reliable traasmission method are increasing. The terminals provide reliable input/output devices into other applications and systems using the current CCITT recommendations. Continued growth in the number of terminals, including the domestic environ­ment is expected.