One of the most important techniques introduced into the recent facsimile is redundancy-reduction coding. The CCITT already standardized the coding schemes to be employed in Group 3 and Group 4. There are, however, left for further study the optional non-information-preserving coding scheme for black-and-white pictures and the coding scheme for multilevel and color pictures. Much work has been carried out with respect to these kinds of coding, including pattern-matching coding for black-and-white pictures and various information-preserving and non-information-preserving coding for multilevel and color pictures. The Group 4 apparatus is a new generation facsimile apparatus, which is mainly operated on public switched data networks. This kind of facsimile apparatus features higher resolution and error-free reception, and has the teletex-facsimile mixed mode capability as an option. The most important technical problem in the standardization of the Group 4 facsimile is the communication protocol which has been developed based on the existing teletex protocol. Facsimile communication is carried out not only on general public switched telephone or data networks, but also on specialized networks dedicated to it. Some sorts of communication processing such as speed conversion, automatic appending function, repeated delivery attempt, etc., are incorporated into these networks. The development of facsimile equipment has also shown progress in these few years. For example, a very compact apparatus has been developed using a new contact type imager and a codec built by special-purpose LSIs. The press fax apparatus employing flat-bed scanner and multicolor facsimile apparatus have also been put into market. This paper describes the outline of recent advances in facsimile, including the above-mentioned items.

Incremental generation of straight lines and circular arcs is important in various fields such as graphic displays, digital plotters, and numerical control systems. An improved algorithm of incremental curve generation called a modified displacement comparison method (MDCM) is proposed.