TRS-80 strings; biofeedback and color photos. Stephen B. Gray.

Full Text: COPYRIGHT Ziff-Davis Pub. Co. 1984

Checking out Route 67 on the Tandy map, we see it leads to a tired switch, the Bio Detector program from Computerware, two kodak systems for photographing CRT graphics, and a third short star-twinkle program. The Tired Switch

You have just written some text with a word processing program, and you want to save it. So you type:

S XYZ/SCR or something similar. But instead of the text being written to disk, you get this message:

Write Protected Disk

So of course you take the disk out of the drive to look at it, and of course there is no tab covering the write-protect notch, because you didn't put one there.

So what happened? With a bit of detective work, you find you have been a little lazy. Instead of taking the disk completely out of the drive at the end of a computer session, you just opened the drive door, and pulled the disk out half an inch, so the data don't get scrambled when you turn off the TRS-80.

(At least this is what we have all heard for years is supposed to happen, and all the manuals warn: "Do not place a diskette in the drive while you are turning the system on or off," or words to that effect. Do it often enough, though, and you'll have trouble booting up Basic, or your word processing program, or whatever is on the disk.)

Leaving a disk partially out of the drive is a fairly common practice. We do it often when we use one disk more than the others; we leave it in the drive because it is probably going to be used at the next session.

There is a little microswitch inside the drive that senses whether the write-protect notch is covered or not. Listen as you push a disk into the drive: the microswitch clicks on as it detects the far end of the disk jacket; then clicks off as it drops into the notch (assuming there is no tab covering the write-protect notch).

Now pull the disk forward half an inch; the microswitch clicks on, and it will stay on for hours, or maybe days, until you push the disk forward again.

These microswitches are guaranteed by the manufacturer to operate may thousands of times without error. But just figure out how many times you click that switch in a week. After several years, the write-protect switch is going to get a little tired, and if you insist in leaving it in the on position, it may just decide to stay that way. Which is why you get the Write Protected Disk message; the computer has no way of telling the difference between a tired notch switch in the on position and a write-protect tab.

The next time you turn off your TRS-80 (or any other computer), take the disk all the way out of the drive first. Otherwise you may eventually have to take your machine to a Radio Shack Computer Center to have the microswitch replaced. The current cost of that operation is $30. Bio Detector

You've probably read or heard about bio feedback monitoring, how it can measure the stress you're feeling, and how you can use it to lower your stress level.

Bio Detector from Computerware is a $34.95 combination of hardware and software that graphs your galvanic skin response on the screen of a 16K Color Computer.

The hardware consists of a Velcromounted, adjustable skin sensor with silver contacts, attached to a small "monitor box," which plugs into the joystick jack of your Color Computer. First you load the Biograf program from tape as you wrap the sensors around the first two fingers of one hand.

Then you set four variables, which are displayed on the bottom of the screen. The Scope speed can be set to slow, medium, or fast. The Trace can be displayed as a line or as dots, whichever you prefer. Audio can be turned off, or set to variable (a changing tone that gets higher as the trace gets higher) or fixed (a beep that sounds more often as the trace gets higher). Mode may be set to Bio (the bio feedback mode) or to AA (for the Anxiety Attack game).

Although the manual dosen't mention it, you use the spacebar to stop the trace, so you can change any of the settings, which depend largely on personal preference; I like a slow line-trace, with variable beep. How It Works

Bio Detector measures skin resistance and converts this to an analog signal, shown on the screen in an elaborate and colorful display (Figure 1). According to the theory, the more stress, the higher the numbers sent to the computer. Bio Detector is said to "help you learn to lower your personal stress level, to observe your reaction to questions or other stimuli... It can also be used as a simple lie detector."

As the plotting starts, you adjust the sensitivity control on the monitor box until the trace is near the middle of the screen, vertically. This is the most important adjustment; too high or too low, and the trace flattens out.

To check the operation of the Bio Detector, take a deep breath and hold it for as long as you can; this causes stress, and the trace on the screen should rise dramatically.

According to the manual, bio feedback means amplifying any function of your body, to make yourself aware of something you ordinarily might not be aware of. You could, for example, amplify your heartbeat, and then learn to speed it up, or slow it down, at will. The Bio Detector measures skin resistance, which is inversely proportional to body stress. The amount of stress it senses is displayed on the screen and heard as a changing tone, so that you can learn to lower (or raise?) your "personal stress level."

The manual claims that "bio feedback has been used to cure people with chronic headaches, ulcers, and many other stress-related problems. People with high stress jobs have learned to relax and deal with their work without as much tension." No suggestions are given on how to relax.

Personally, I found that, with a little practice, I could lower the trace level a fair amount, but not always when I wanted to.

The Bio Detector can be accessed from a Basic program, because the Color Computer sees it as a joystick. If the Detector is plugged into the right joystick jack, look at JOYSTK(0). A four-line Basic program is provided to let the computer look at the right joystick port and "make an appropriate tone." Lie Detector

Put the skin sensor on another person's fingers, allow him some time to relax, then ask a question. According to the manual, "if the trace does not move up or down very much, the answer was probably the truth. If the trace moves about a half an inch or so, the person may not be telling the whole truth. If the traces moves up more than an inch the answer is probably not true at all."

The manual continues with a disclaimer, "Please remember that this is not guaranteed to produce 100% accurate results. You shouldn't take the responses of the person too seriously. "We don't want to cause any divorces.)" The magazine ad goes even further: "This is a toy. Results not admissible in court." Anxiety Attack Game

In AA mode, the computer is much more sensitive to upward movements of the trace. The idea of the Anxiety Attack game (Figure 2) is to get somebody to put on the sensor, then see if you can "get the person ... to react. Try asking how his car got that huge scratch in it, or make a funny face. (Tickling is not fair!) Do anything you can to make the trace go up." Anything?

The manual suggests you "try this at your next party ... to see who can hold out the longest without making the screen flash"; flashing means the display turns on and off, alternating rapidly with a blank screen. Anxiety Attack "works especially well when there are a lot of people around. This is a good test to see if you really have learned stress control in the Bio Feedback mode."

The stress level in Anxiety Attack is much more difficult to control than in Bio Feedback mode, because of the increased sensitivity. Those Color Photos

The color photos illustrating the Bio Detector program were taken with Kodak's Instagraphic CRT Imaging Outfit, which makes instant color-print copies of images displayed on 12" or 13" CRT screens.

The Instagraphic Outfit (Figure 3), introduced in 1983, consists of two basic parts: a modified Kodamatic Champ Instant Camera with a close-up lens; and a Kodak Model 12 plastic CRT cone. Also included are two 10-exposure packages of film, a filter to provide "warmer" prints, and brackets for adapting a 35 mm single lens reflect camera of the cone.

Setting up the Instagraphic is simple: load the camara; mount it on the cone; position the cone against the face of your monitor or TV screen; and hold down the shutter release until you hear a click. The click is from the camera's automatic exposure control, which adjusts the exposure time for screen brightness.

Because tube face sizes and configurations vary, the cone is designed to fit against the frame around the tube, or against the cabinet. Four rubber bumpers are mounted on the corners of the cone-flange face, to provide a nonslip contact between the cone and the CRT frame, and to space the cone flange away from the CRT frame or cabinet.

The outfit also includes foam strips for creating a light baffle between the cone flange and CRT frame. However, the strips are useful only if the room lights are to be left on while the CRT screen is photographed.

With only the bumpers applied to the cone flange, the camera will record the full area of a 12" (diagonal) CRT. With a 13" CRT, the cone will slightly crop the bowed sides of the CRT face; to show the full screen, spacer pads can be added to move the camera back. For the 13" screen of Radio Shack's color TV, four spacers were added under each bumper.

After a few trial exposures, the Instagrahic Outfil is easy to use. Once you've figured out just where to place the cone, all you do is push the button, release it when you hear the click, and wait for the color print to emerge from the camera. The 12-page manual provides plenty of detail on positioning the cone, optimizing focus, adjusting exposure, and using a 35mm camera.

According to the press release, "black-and-white duplicates of the color prints can be made with any high grade office copying machine for inclusion in written reports."

The suggested list price of the outfit is $190, although it can be bought in New York for $168, from the industrial division of one of the large camera stores. Second-Generation Imager

Offering a selection of cones in different sizes, Kodak's second-generation Instagraphic CRT "print imager" was announced in May 1984. The modular system offers cones in 9", 12", 13", and 19" sizes.

The new print imager (Figure 4, foreground) has four basic components: a new Kodak Instagraphic camera back, box-shaped "print module," CRT cone, and cone "adapter." The background shows the four adapters, which slide into the cone, and are held in place with a pair of metal snap fasteners.

A bracket is provided for using a 35 mm SLR camera in place of the camera back and print module. A filter-holder is also provided, in case the user wants to color-balance the phosphors of some CRTs.

The camera back of the new print imager is "designed for professional use," according to the press release. The new back and print module will be featured in a professional product later in 1984. The print module includes the shutter and a variable focus lens, and partially corrects for screen distortion.

The new print imager has no automatic focus control, so "one or two test exposures may be required to arrive at the best exposure for the brightness level of the particular CRT."

A close look at the photographs shows three words under the Kodak logo on the camera back and cone: Made in Germany.

Exact list prices have not been established at this writing, but the basic imager will be less than $300, and the cone adapters will be less than $40 each. The original outfit will continue to be available.

There are several other camera-and-cone systems for photographing CRT graphics, but none I've seen is as inexpensive as the Kodak Instagraphic printmakers. Short program 51: Twinkle 3

From Ottawa, Ontario, Canada, Tammy Dunlop sent a CoCo version of the twinkle program (Nov. 1983, p. 330), with this letter:

"I finally have gone out and bought myself a TP-10 printer for my Color Computer. I'm not fussy on the thermal paper, but for the price I am willing to put up with it till I can afford something better.

"The program is one I thought of while allowing my mind to wander off work the other day. It uses an array setup of remember the pixel positions, and scanning through it gives the twinkling effect, along with a random selection of pixels on the screen that keeps changing. If you have a good imagination (like the old astronomers) you may see some of the constellations form before your eyes."

Run the program in Listing 1 on a Color Computer and 20 pixels will appear at random locations on the screen, in random colors. As soon as the 20th one appears, the stars--one by one--are randomly turned off and then right back on again, accompanied by a rapid, random note melody that may drive you bonkers within minutes. Each star disappears after several minutes (and several dozen twinkles; actually, 60 twinkles), to be replaced by another star elsewhere on the screen.

Tammy's REMs include: "Twinkle Twinkle, for TRS-80 CoCo 18K Basic. The larger the number for PIXEL, the more stars and the slower they twinkle. LOOP=1 to 3 gives three flashes to each star before going on to pick another random star from the many on the screen. Maximum number of stars is 60, due to size of arrays. Line 34: position in array. Line 36: number of stars; max 60. Line 38: twinkle test. Line 90: Subroutine--set to twinkle, and reset array pointer."

Lines 50-56 set pixels at random locations on the screen in random colors. Lines 60-65 count the number of pixels; if there are fewer than 20 (or whatever number line 36 is set to), line 70 jumps the program to line 80, which jumps back to line 40, to keep on setting pixels.

If the pixel count goes over 20, line 65 calls the subroutine in lines 90-92, which resets the pixel counter to one, and sets TT to one. Now lines 71-79 come into play, to turn off--and right back on--each of the 20 pixels, three times each, in rotation as determined by their locations in the arrays. Also, a random melody is created by lines 73 and 75.

After the third off/on go-around (60 twinkles' worth, or three loops times 20, or LOOP*TW), the program jumps back to line 40, to turn off a pixel for keeps. A new pixel is turned on (to provide a little variety), and the sequence repeats.

In other words, after the program has reached line 79, a pixel is turned off permanently, and a new one is set by line 56 every three twinkles. To prove this, add:

58 PRINT @ 0, X;Y;Z and watch the three numbers change rapidly at first until 20 pixels are set, then change only after each round of three twinkles. the program can be adapted for a TRS-80 Model I/III/4 by dropping the Z or AZ part from lines 32, 56, and 76; dropping lines 54, 73, and 75; changing the 62 in line 50 to 127; and the 30 in line 52 to 47. The "twinkle" will be faster than on the CoCo; these stars don't actually turn completely off, as they do in color.

The TRS-80 Model 4 has the same SOUND statement as the CoCo, so you can leave in lines 73 and 75 if you have a 4.