HP Deskjet B/W and Color
========================

- If the printer does not draw in paper and so does not print, then 
  in some circumstances this could be due to a paper jam (the mechanism 
  can not feed in the sheet). Remedy: Put the paper stack in again.

HP Deskjet 500/500+ (B/W) & HP Laserjet II
==========================================

- HP Deskjet and Laserjet II are almost identical in their control 
  commands, they differ only in their margins.
- The prototype that is used for both printer families contains a small 
  trick to reduce the top margin still further (see also ATTENTIO.TXT):
     - The top margin is set right to the top, as is also the printer-
       internal graphics cursor (with this all addressable margins are 
       reduced).
     - When printing a page the graphics cursor is 'run down' by the 
       number of lines that are specified as the top margin, in order to 
       bridge the difference between the addressable and printable 
       margins.
     - The first print byte is then - providing the top margin is set 
       correctly - printed at the top of the printable area.
     - If this mechanism was not built in like that, then either the 
       addressable area would be smaller than the printable one, or some 
       print data would be cut off that are addressable but cannot be 
       printed.
  IMPORTANT: This trick does NOT work with the Deskjet, as with this the 
             addressable and printable areas are equal.
             Therefore in HP_DJ500.CDD the print cursor is 'run back' 
             again in the code #HEIGHT.
- The HP Deskjet, unlike the HP LJ II does not contain a page memory 
  and therefore is not able to print multiple copies itself; these have 
  to be built up anew by Calamus depending on the space in RAM.

HP Deskjet 500C/550C
====================

- These two colour Deskjets differ only by the use of a fourth colour 
  level (black), that thanks to stacks of soaked-through paper is 
  something to talk about. This problem is connected above all with the 
  control curve settings in the LIN module. There the black extract 
  portion has to be reduced by flattening the corresponding curve. 
- Recently (from 26.06.93) both drivers contain some optimizations, 
  because FINALLY the manual for the 550C has become available to me.
  In the GRAPHMODE code, grey balancing is now switched on as well (only 
  with the 550C - results in an improvement of greyscale reproduction by 
  reducing the cyan values) as well as setting the print mode to 
  bidirectional and the graphic quality to 'high'. In addition both 
  drivers contain a dialog that can be called via the 'Farbkorr.' button 
  in the Calamus Print dialog. Here you can set the colour depletion and 
  shingling (interlacing) to reduce the amount of coloured ink brought to 
  the paper. The values recommended by HP for various paper types 
  (normal/HP paper, transparency foils, HP glossy paper) can be chosen 
  here. Nevertheless as before one should attempt to use the Calamus 
  control curves (LIN module) to reduce the amount of colour printed,
  as HP depletion and shingling are only provided as an emergency for 
  software that does not use colour correction. Important: The depletion 
  operating modes 25% w/gamma and 50% w/gamma with gamma correction are  
  not available for the 500C.
- The data transfer is many times faster than with e.g. a Canon BJC-800, 
  as here - as with the HP LJ III - TIFF compression is used for graphic 
  data transfer. In addition the Deskjet Color models are fitted with an 
  extremely fast Centronics interface, so that one can output on TTs with 
  'Parallel' (fast direct print output) instead of 'Other'.
- This driver is only laid out for 300 dpi.
- Although the driver does not have empty line optimization for multiple 
  empty lines, for each empty line (colour layers taken separately) it 
  only sends 8 bytes (hardly a loss in speed).
- The minimum printing margins can be set

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