101 Stupid LaserJet Tricks

When I was moved into my new office downstairs, it was located in a space behind what used to be the reception area of the building. The front door was locked from the inside, and visitors would enter a door slightly off to the side and climb stairs to a new reception area.

When anyone visiting would come back down those stairs they would sometimes forget that they came through the side door. Instead they would go out the original glass door, which was an inner door and an outer door. The first door had a lever you pushed to unlatch and open the door. This was locked so that if you passed through this door you couldn't come back in. Once through this door there was another door right there. This had a locked bolt, but you could just unlock the bolt and get out, and invariably this is what people did.

Then I had this idea for a prank. Using the LaserJet printer I printed in great big letters READ THIS. Then below in a tiny 4 point font I printed "If you can read this then you are trapped!" I drew an arrow from the large words to the tiny words by hand. I hung this on the wall between the two glass doors.

Weeks later I was in my office working and I heard some banging and the sound of someone calling out. I went out to find out what was going on. Shock and amazement overcame me when I saw this fellow between the glass doors, banging with his fist and calling for help! He had read the sign and believed it! I laughed and opened the inner door for him and explained that he really wasn't trapped at all. So I showed him how to unlock the bolted outer door. Unfortunately he didn't think this was funny at all. He didn't smile or laugh but he just left without saying a word. Perhaps he was humiliated that he had fallen for the trap?

I was very pleased to see that someone had read the sign and believed it. This was absolutely priceless. Looking back at this prank I should count myself lucky that I didn't get in trouble.

Our First Laser Printer

We decided to purchase a laser printer so we could print bill of materials sheets for each job. I managed to find a used HP LaserJet cheap. This was the original LaserJet printer model and had only 128K of RAM. This was fine, except if you wanted to print graphics. You could not even draw a half page of black and white graphics with 128K. This also meant that there was very little room to load fonts into the printer. The saving grace was that there was a font cartridge slot. I bought one of those super font cartridges that had lots of fonts. It turns out that we really only needed one font. I don't remember which one we used, but it was a small monospaced font.

The printer had a serial port, not a Centronics printer port. Normally this would have been considered a limitation, but this was perfect for our shop floor control system which I was building around Arnet multiport RS-232 cards.

I needed to learn just a little bit of Hewlett Packard's PCL (printer control language) to make the LaserJet do its thing. I wrote some code in Smalltalk to drive the printer. Depending on how complex the board design was, these bills of materials sometimes had a lot of information on them. It was somehow very satisfying to produce software that would drive a printer elsewhere in the building. I had never done that before.

The printer was located up in the engineering department, and after they designed a circuitboard for an order they would fill in some fields into the shop floor control system and print out the bill of materials on the LaserJet.