Two CCITT meetings are likely to see lively debate on the future of facasimile. The plenary session of Study Group 1, which deals with network services, takes place from April 24 to May 3, and later that month, Study Group 8 – telematic interfaces – gets together. Both committees will be discussing the relative merits of Group IV facsimile and the pretender to the throne, Group IIIbis. Group IV fax has been around since 1984 and perceived as the natural choice for ISDN with a number of manufacturers already producing kit. But its detractors argue that it has a string of shortcomings that need to be sorted out. In particular, Lester Davis, chairman of the British Fax Industry Consultative Committee (BFICC), points out that it has been criticised for the inefficient way in which it uses the full-duplex capabilities of ISDN. Although the network is capable of signalling faults and requesting retransmission at the same time as the other fax is sending data, Group IV retains a page-based error checking system that sends acknowledgements only at the end of a page. This is particularly inefficient over satellite links where transmission delays can cause a wait of several seconds – not insubstantial, when an entire page goes through a Group IV facsimile macchine in around three or four seconds.
Alternative standard
The past 12 months have seen growing support for an alternative standard. Currently it has no name, although some call it Group IIIbis, but Davis prefers Group III at 64Kbps – G3at64. Extensions to the Group III standard enable it to send data at 14.4kbps, but the G3at64 protagonists advocate speeding it up some more and adding an ISDN interface. As regards the full duplex question, they suggest that requests for retransmission be sent concurrently with data transmission if required. While they are not suggesting that Group III machines will be substantially cheaper than Group IV, they argue that the G3at64 approach will make it easier for faxes attached to the ISDN to interwork with the public switched telephone network. As might be expected, those companies and countries that have invested heavily in Group IV manufacturing are none too keen to find others proposing an incompatible standard. The likelihood is that the committees will split down broadly geographical lines. Backing G3at64 are the UK, the US and manufacturers from the Pacific region other than Japan. Meanwhile Japan, France and Germany are said to be supporting continued development and support of Group IV. A consensus is needed if the industry is to avoid a commercially damaging re-run of the war between the VHS and Betamax standards in the video cassette recorder market. However, there are signs that some groups have made up their minds already and industry sources suggest that South Korean manufacturers are now committed to producing G3at64-based machines, come what may.
