Houston Instrument
DMP-61 pen plotter

    This is an example of a reasonably modern (1987) plotting (drawing) device. As in almost all older (or "budget") plotting devices, this machine functions by moving a pen and paper in two dimensions to produce drawings.

    While some plotters moved the pen in both axes, this device took the much simpler (and more common in later plotters) of moving the pen in one axis and the paper in the other. By carefully controlling these movements, it was possible to produce drawings of exceptional quality. Another famous plotter to use the "Pen=Y, Paper=X" technique was HP's 7580 series.

    For the most part, drawings were produced using disposable liquid ink pens although ball-point, as well as felt tip pens, were available. The line quality of the liquid ink drafting pen was excellent.

    Only recently have Xerographic techniques been able to approach the output detail of these devices.

    Of all the queries I receive, by far the most frequent one is: "Do you know where I can get drivers or supplies for my plotter?"

    If your machine has the HPGL option, which all later- model DMP plotters do, you can use the Hewlett- Packard 7580B (for DMP-61) or HP7585B (for DMP-60) ones. I know of no source for "native- mode" DMPL drivers.

    Supplies for these devices can still be obtained; I suggest calling your local computer supply outlet or graphics arts supply. Your best bet will lie with places that specialise in CADD (Computer Assisted Design and Draughting) supplies.

    If you've just acquired one of these devices, you can run a self- test on it by following these instructions:

1. Load the paper thusly (it's important to do this correctly as the machine counts on it to auto- size the media):
   1. Place the paper with the right- hand edge flush with the white lines on the platen
   2. Ensure that the front edge is aligned with the groove on the front of the platen
   3. Lower the rubber grip- wheels to lock the paper down
   4. Press the "Load" button
2. Ensure you have a working pen in the holder.
   If you have the pen changer option, raise the holder to get it out of the way.
3. Make sure the plottter is in the "Local" mode.
4. Press the "up" and "down" arrow keys simultaneously.
   Expect the test to take at least ten minutes, and possibly more.

    While the DMP-6x series machines run "natively" in DMP mode many came with the HPGL option which allowed them to emulate a Hewlett- Packard HP758x series plotter. Running the machine in HPGL mode will allow the use of the HP758x drivers included with Microsoft Windows.

    Here's how to get the plotter into HPGL mode (this is an option, remember, so your machine may not support it!):

1. Make sure that media is loaded into the plotter by following the above instructions.
2. Press the "Enter" key on the front panel.
3. Press the "Clip UR" key.

    This puts the plotter into the HPGL setup mode. Selections are made by using the "left" and "right" arrow buttons on the panel to place the pen over the desired object and by pressing the "Enter" key. My recommendation here is to select "Help" immediately; the plotter will print out operating instructions for the setup operation.

    When configuring your plotter you must ensure that your comms parameters match those on your host system exactly; this is where most people (myself included) stumble badly. Some experimentation will probably be required before a working configuration is arrived at. Once the configuration is complete it must be saved to the plotter's non-volatile RAM; do this by pressing "Clip UR" followed by "Scale UR".

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