Black fax to harass large institutions or government departments, to retaliate against the senders of junk faxes, or merely as simple pranks. The basic principle of a black fax can be extended to form a "black fax attack." In this case, one or more sheets are fed halfway through the sender's fax machine and taped end to end, forming an endless loop that cycles through the machine. Not only can solid black be used, but also images which will repeat endlessly on the receiver's machine until its toner runs out. The introduction of computer-based facsimile systems (combined with integrated document imaging solutions)
Fax tone into a variable current that controlled the mechanical movement of a pen or pencil to reproduce the image on a blank sheet of paper on an identical drum rotating at the same rate. In 1985, Hank Magnuski, founder of GammaLink, produced the first computer fax board, called GammaFax. Such boards could provide voice telephony via Analog Expansion Bus. Although businesses usually maintain some kind of fax capability, the technology has faced increasing competition from Internet-based alternatives. In some countries, because electronic signatures on contracts are not yet recognized by law, while faxed contracts with copies of signatures are, fax