There are two types of PostScript Fax jobs. You can able to select between transmission of PostScript Language data and raster data. Subsequently, PostScript Fax printers may send faxes as raster data, or when communicating with another PostScript fax printer they may send PostScript language data. Either way a PostScript job is sent from the client to the printer to be either transmitted or rastorized then transmitted.
Single destination
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A fax transmission in raster form to a single destination will be made in a single call if there is sufficient storage to hold all of the raster pages of the job. However, the transmission may be broken into multiple calls if there is not sufficient storage. If the storage of the raster pages is exhausted, then a call will be made before rasterization is complete. Transmission and raterization will then take place simultaneously. If transmission succeeds in sending all prepared pages before raterization of the job is finished, the call will end. A subsequent call will be made either when all of the rasterization is done or when storage is again exhausted. Thus, a transmission may be broken up into multiple calls. It is also possible that when transmission and raterization are taking placed simultaneoulsy, rasterization keeps up with transmission. In this case, this transmission will be the last call for the job. If the storage in use is a disk, there will typically be sufficient storage for all of the raster pages of a job and the fax will be transmitted in a single call.
It is possible to request that a transmission take place at a particular time. These delayed transmissions, of course, are made with a single call. Since the pages of a raster job are prepared when the job is submitted, all of th pages of a delayed raster transmission must fit in storage, otherwise, the job will fail.
Multiple destinations
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For a raster fax, the common body is rasterized and compressed only once. For a PostScript language file transmission, the out-bound file is assembled only once. Then, in either case, the previously prepared material is transmitted multiple times - one copy to each different recipient specified. Thus, one requirement for a broadcast job to succeed is there must be sufficient storage (RAM or disk) to hold all outgoing files that form the fax. Broadcast transmissions are not broken into multiple calls.
Resolution
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Raster data - the specification for CCITT fax resoution is approximately,
but not precisely, 200 dots per inch (dpi). A non-integral
resolution would drastically decrease the efficiency of the
PostScript interpreter. More importantly, the precise scaling
generates moirÄ patterns in halftones rasters, that may be
prevented by rounding. Therefore, a rounded scaling to 200
dpi is performed.
PostScript data - PostScript file transmission to another PostScript
compatible faxscimile is output at printer resolution
(300 dpi or better).
faxopsexec
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faxopsexec is an exec, that pushes the Fax Options dictionary onto the stack, in order to execute the PostScript operand that precedes it.
Adobe uses faxopsexec to access predefined PostScript procedures implemented in an invisible, inaccessible dictionary. These ProcSets (dictionaries containing procedures) are not documented as they are either confidential, likely to change, reserved, have functionality useful only to Adobe, etc.
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