Category Archives: Identify It!

Identify It Challenge for 7-26-2012 Answer

Sorry for the delay in posting this, its been a very busy late summer for Harris Educational!  Mostly good stuff, but enough of that, on to the answer.

Here is the original video “Identify It Challenge” as posted on 7-26-2012

And now here is the answer:

Read/Write Head Assembly from Diablo Systems Series 30 Disk Drive

Read/Write Head Assembly from Diablo Systems Series 30 Disk Drive
Shown with late 1990’s Iomega Zip Disk for Comparison

This assembly is the read/write head from a Diablo Systems Series 30 Disk Drive manufactured around 1976.  The drive was not a traditional Hard Drive (or fixed disk) but instead took IBM 2315 disk cartridges that were about one foot in diameter and could hold a grand total of 1.25 MB!  (the later series 31 model used a disk that could hold 2.5 MB).   A photo of these disks can be found here.

The mechanism has a synchronous drive motor (with run capacitor) built into the bottom of its cast housing.  This motor drives a shaft with integral pinion gears that engage a rack gear that can move the drive’s double sided read/write heads back and forth along the disk surface.  The large solenoid and damper open and close the read/write head around the cartridge after it has been inserted into the drive.  The green marked disk on top  corresponds to the tracks on the disk itself and was used to mechanically orient the drive heads in order to synchronize them to a standard disk during manual alignment.  The green disk also contains a kind of rotational position sensor that sends pulses back to the controller based on its movement.  The micro-switches act as end-stops to keep the heads from being sent past their absolute physical end-stops.  The whole drive head assembly weighs in at about six and a half pounds.

You can see a pictures of the whole drive AND read about how it works through repair and maintenance manuals at the following links:

This drive (and two others) came into my possession around 1990.  My high school electronics lab received them as a junk donation much earlier in the mid 1980’s and they’d sit in storage taking up space until then.  My electronics teacher gave them to me when I helped him clean out the storage and I then dissected them to learn how they worked and for parts.  They were much too large and heavy for me to keep intact at the time, though I did keep the read/write mechanism intact knowing that one day it might come in handy for some kind of display, and sure enough it fits into the Identify It Challenge nicely!

This assembly (or rather the disk drive that it came from) has some significance in the history of computing because:

  • It is a predecessor to the Floppy Drive
  • It helped to show the value of removable random access storage (not just linear access storage like tape)
  • It was a peripheral for mini-computers and as such was an add on (not necessarily manufactured by the mini-computer maker) and as such helped to bring in the idea of standards and interchangeability.
  • It was used as storage for the Xerox Parc computer, the first computer with a graphical user interface and a predecessor to modern PC’s

Thanks to everyone who made guesses over on Facebook.  The  first person to make a correct guess was Duffy Toler, guessing it was a read/write head assembly.  John Sucilla came closer by guessing it was from a DEC RK-05 disk drive.  (in reality Diablo Systems was bought out and became a part of Xerox and then later Xerox sold these drives to Digital Equipment Corporation where they were used as peripherals for their PDP line of computers.)

Stay Tuned for the Next Identify It Challenge!


Identify It! Answer for 10-13-2010

Thanks to everyone that played this week’s Identify It! Challenge. For this week’s challenge we asked fans to guess the informal name, scientific name, give several facts, and identify one unique feature of this specimen of spider. Here is the original photograph:


Writing Spider : Argiope aurantia
Writing Spider : Argiope aurantia

The answers are:

Informal Name: Writing Spider (AKA Black and Yellow Garden Spider)

Scientific Name: Argiope aurantia


  • This spider is called a writing spider because it often creates zig-zags (that look like the letter Z) or X’s or other patterns that look like letters. It does this because it often weaves very large webs and the patterns make the web visible to birds, squirrels, and other animals that might knock its web down.
  • Although incorrectly drawn in the cartoon, Charlotte from “Charlotte’s Web” was a writing spider!
  • This spider will bite human beings if provoked but is not aggressive and its venom is usually not very potent. (its still a good idea to leave all spiders alone though)
  • Argiope aurantia often leave an egg sack with thousands of eggs at the end of the fall season.
  • The size and complexity of its web are a good indication of how well fed it is.
  • Males are small and uninteresting marked, often building a small web adjacent to their female mates. Females are much larger (on the order of 3 inches in diameter) and are brightly marked with yellow spots and patterns on their abdomen and back.

Unique to this specimen: If you look closely at the photograph you will notice that this spider only has seven legs. It isn’t clear if the spider lost its leg at some point or if it was born without it.

This specimen has lived for at least the last three years on the side of the Sylvan Learning Center in Burlington NC. (As one fan pointed out its interesting that a “writing spider” would take up residence at a learning center.)

More Higher Resolution photographs can be found at the following link:

Click Here for more High Resolution Photographs

or also at our “photo” tab at our fan page on facebook (


Belly View (through the web)
Belly View (through the web)
3/4 Side View in Web
3/4 Side View in Web

Thanks to everyone for playing this week’s Identify It! Challenge. Stay tuned for the next one!



Identify It! Contest (3 ways to win)

Harris Educational is offering a free tee shirt as a prize in our Identify It Challenge! There are three ways to win. We will be giving a free tee shirt to the 1500th fan of our Fan Page on Facebook. Once we reach our 1500th fan we will pick one of our other 1499 fans at random and give them a free tee shirt as well. You can also win by sending us your own photograph of an interesting science or technology item that we can use for a future Identify It Challenge. If we pick your photograph to use then you also win a free tee shirt.

How to Play:

Like our fan page and become a fan (  Help us get more fans by suggesting our page to everyone on your friends list. We want to grow by word of mouth, not by paying for advertising so we rely upon our fans to spread the message. We’ve found that the best way to get people to join is to use the “suggest to friends” link that can be found under our profile picture on the top left hand side of the page. You can also use the “share” button on any story to post that story to your wall (or to share the page to your wall). If you don’t like that then just telling your friends by word of mouth is always great. Even if you add just one fan you are helping us out a lot!

To submit a photograph for use in our identify it challenge simply send the photograph as an attachment to ben . harris @ harris – educational . com (take out the spaces, and notice the . and the -) Along with the photo please send a description of what the item is, how it worked, and hopefully a story about how you got the item or where you took the picture. The item should be something that many people wouldn’t interact with knowingly on a daily basis but not something so obscure that only you and your sister have ever seen one. In other words we don’t want to stump the world but rather teach people something new about the scientific and technical world around them and have a little fun in the process.

By sending us a photo and story you are giving us permission to post that photograph and story on our Fan page, on our Blog, and to promote via other online means.

This Week’s Identify It Item!

"Vacuum Tubes are Cool" Tee Shirt by Harris Educational

"Vacuum Tubes are Cool" Tee Shirt by Harris Educational

In the mean while, here is an example of one of our Tee Shirts, our latest design from our store on Printfection. (see

Until we get some fan made identify it pictures THIS is your identify it picture for this week. Yes these are vacuum tubes… but can you identify what kind? What they were for? Where they were used? Can you ID the part number or brands? (show your support of Harris Educational and share this tee shirt and this contest with your friends!)  Submit your answers to the comments for the photo on our fan page.

Stay tuned for answers about these tubes AND for annoucements of winners to the contest.

Chances of winning are roughly 2-# of  submissions for Identify It that we use out of 1500+ (pretty good odds).

Thanks for Playing and thanks for being a fan of Harris Educational

My Visit to the FREEDM Systems Center (part 1)

My Visit to the FREEDM Systems Center (part 1) and the answer to our Identify It Challenge from 7-7-2010

On July 7th 2010 I was the guest of the FREEDM Systems Center at North Carolina State University where I gave a presentation to a group of high school students and teachers about “Engineering, Energy, and Edison.” The presentation included a demonstration of my Reinventing Edison: Build your own Light Bulb kit that was very well received. After the presentation I was treated to a guided tour behind the scenes at the center.

The Keystone Science Center (NCSU) home to the FREEDM Systems Center

The Keystone Science Center, home to the FREEDM Systems Center

This is the first of a two part article about my visit focusing on my educational presentation. It will also reveal the answer to my “Identify It Challenge” from 7-7-10 that by design was integrated into my presentation. The second part of this article will be posted soon and will focus on my tour of the FREEDM center.

Light Socket Electrical Adapters (Circa 1930's/1940's)

Light Socket Electrical Adapters (Circa 1930's/1940's)

The above picture was the “Identify It Challenge” from our fan page on Facebook ( from 7-7-2010. After introducing myself, sumarizing what I was going to be talking about in the presentation, and teasing the audience with a few vocabulary words to look out for I passed these objects around the room and asked everyone to think about what they were, what they were made of, how old they might be, and what they were used for.

The items are (from left to right):

1) A light socket adapter (with standard Edison style screw base and two non polarized non grounded electrical outlets) This adapter allows a bulb to be used simultaneously while other electrical items are plugged into the adapter.

2) A light socket adapter (with standard Edison style screw base and one non polarized non grounded electrical outlet) This adapter does not allow for the simultaneous use of a bulb while an electrical item is plugged in.

3) An electrical outlet multiplier (makes one plug into three) non polarized and non grounded.

All three of these items are made of Bakelite plastic and were manufactured at some point in the late 1930’s or early 1940’s. Bakelite was one of the first natural plastics and was used to replace wood, paper, and other less suitable materials as an electrical insulator in early electrical devices.

So why did I include these items as the opening of my presentation about energy and Edison and why did I also choose them as the Identify It item for the same week? The answer lies in the use for these items and the circumstances that lead to the need for that use. That need also exists today, simply in a different form.

So why were these items needed? Edison created a demand for electricity to be brought into homes because his light bulbs demanded a D.C. Supply from HIS electrical power stations. Before the light bulb there were no electrical appliances or devices in peoples homes. So houses and buildings were retrofit for wiring. Later, after A.C. Power won out over D.C. in the “War of the Currents” homes were still being retrofit.

The first wiring was simply for electrical lighting, the only electrical device you could buy for a home. Each room may have had a single light switch leading to an overhead light fixture and no other connections. Soon the commercialization of electric motors and heating elements spawned hundreds of devices that people wanted to use. Later in the 1930’s and 1940’s people added electronic devices like radios to the growing list of electrical items they needed to plug in.

So a home owner found themselves with a hand full of gadgets and only one electrical outlet in a room, and that was taken up by a light bulb! As a result these adapters were invented. With them you could plug a device into the overhead light fixture and the miracles of modern conveniences were at peoples fingertips. Miracle at least until many home owners suffered from electrical fires by plugging in too many items and drawing much more current than the simple lighting circuits were designed for!

There are two points to be made here (the reason for my picking these items, including them in the lecture and in the Identify It)…

The first point is one of infrastructure. Edison is not actually the inventor of the incandescent light bulb. He’s credited with the invention but he was not the first. He did make it to the patent office faster than most (even before he had working examples) which is one reason he is hailed as the inventor of the bulb. But the real reason he is considered the father of electrical lighting is because he didn’t just make the bulbs, he created the entire infrastructure needed to manufacture, market, supply, add wiring, supply electricity, and bill for that electricity. He wasn’t selling bulbs, he was selling devices that used electricity. The profit was in selling electricity! In the process he (and his muckers) created fuses, junction boxes, conduits, the light bulb’s screw base, switches, dynamos, power meters and hundreds of other items needed before you could ever see white light stream out of a heated cotton thread.

The second point is about being able to foresee the future and forecast future demand. Edison created a need for electricity and the addition of electrical wiring to homes and buildings. His business model was similar to that of gas lighting companies (early light fixtures were even made of brass and mimicked the gas light fixtures). Edison for all his brilliance did not really foresee the hundreds of electrical devices that people would also want to buy and use. As a result wiring went from a single bulb fixture mounted to the ceiling of a room, to a bulb adapter crowded with cords hanging from that fixture posing a fire hazard, to expanded more modern wiring and the addition of more circuits. Even so we still use power strips (more modern safer ones) to keep all of our stuff going. But with every new device we add more load to the system.

The folks at the FREEDM center that asked me to give the presentation wanted me to focus on energy and on innovation and this is where things all tie together. If you buy a home today that was built in the 1960’s or early 1970’s its not uncommon for a room to have one electrical outlet on each wall (or perhaps not even on each wall). Designers and code makers then assumed you might have a lamp or two, maybe a TV or Radio, and may plug and unplug other gadgets as needed. Today it would be great to have six outlets on every wall because of all of our gadgets. Computers, cell phones, mp3 players, fax machines, phones all the things that need power. Most devices actually run on D.C. power converted from A.C. by an internal power supply or a power brick plugged into the wall. All of this was not foreseen in the 1960’s and 1970’s.

Flash forward and ask yourself… what will electricity supply and use look like in the future? If we do move away from gasoline powered vehicles to electrically powered vehicles then we’ll need to recharge those vehicles (another kind of electrical supply, more outlets… how many? 1? 2? what will the plug look like? Will it be D.C. or A.C.? Will folks have dangerous Y-adapters to split their charging output so that they can charge their own two cars and then also Juniors new car at the same time?)

Its impossible for anyone to fully predict the future. Changes in technology, availability of resources, and millions of other factors make futurism impossible to get right. But the high school students sitting in my demonstration and lecture are going to be the next wave of electricity consumers, inventors and engineers, technicians and educators and so its important for them to try to foresee the implications of their ideas and be prepared for the future in order to prevent the need for things like quick/cheap/possibly unsafe adapters like those pictured above or their equivalent in future technology.

The electrical grid we use today is the legacy of over 100 years of almost organic growth and expansion. Its not to say that reasoning and planning did not go into the design of the components of that grid because in reality it represents a monumental engineering feat that most of the time we can take for granted as we switch on our latest gadget and have that gadget “just work”. But its important to think about energy related issues in our day to day lives. How can we cut down on energy use. How can we stop energy waste? How can we safely and economically expand and create a new smart grid that will adjust to demand. How can we comfortably switch from non renewable centralized generation of energy by burning coal and fossil fuels and move to a distributed system where every home or device might produce as well as consume electricity. All of these questions are being researched at the FREEDM center, and the curriculum taught to students in their program on innovation reflects these questions.

A copy of the presentation slides used for our presentation can be found at our page on Scribd at:

Stay Tuned for Part II and keep an eye out for future Identify It Challenges. (thanks to everyone who attended my presentation at the FREEDM center, and thanks to everyone who played Identify It).

Identify It! Answer for 6-18-2010

Thanks to everyone who made guesses on our Fan Page on Facebook for this week’s Identify It! Challenge.  Here is the item:

Identify It! Challenge Item for 6-18-2010

Identify It! Challenge Item for 6-18-2010

And the answer is…..

Riverside Model 61-9223 DIY Tire Balancer

Riverside Model 61-9223 DIY Tire Balancer

This object is a DIY Tire Balancer used to balance tires for “Economy and Comfort.”  Basically its a bubble level mounted in a rig that is sitting balanced on an interior pointed cone.  A tire is placed over the larger exterior spindle cone and then lead weights can be  added to the rim of the tire to make the tire balance.  Balancing is important to keep tires from oscillating or vibrating due to imperfections in their manufacture.  Balancing tires also helps improve gas mileage and improves the life span of the tire and the wheel bearings not to mention giving a smoother ride.

This particular model was manufactured by a company called “Riverside” and was distributed through Montgomery Ward.  In fact it is a model 61-9223 and based upon the information on the box was manufactured in 1971 and sold for $21.98

Make sure to wash your hands good after using one of these, since tire weights are made of lead!

Identify It! Answer for 6-3-2010

This Identify It! Challenge was a little different than normal. Thanks to everyone who DIDN’T post an answer! I knew when I posted this weeks picture that a portion of our audience would likely know exactly what this object was. Imagine my delight when one fan posted a picture of himself with his very own!

Heathkit Model 336 High Voltage Probe

Heathkit Model 336 High Voltage Probe

This item is a High Voltage probe manufactured by the Heathkit corporation as a build-your-own kit in the early 1950’s. In fact its is a model 336 “Television Test Probe Kit.” It is meant to work with multiple models of their popular vacuum tube volt volt meters. The unit pictured here was bought along with a model V5 Heathkit VTVM kit and originally sold for $5.50 in 1951! It extends the range of the VTVM so that it is possible to measure voltages up to and including 30KV.

What Its For:

This probe is meant primarily for use in servicing cathode-ray-tube based television sets. A CRT works like any other vacuum tube in that a filament heats a cathode which then emits electrons (a.k.a. the Edison effect). Since electrons are negatively charged they will be attracted to, and accelerate towards a positively charged plate. In an ordinary audio or radio tube the plate voltage is anywhere from a few hundred to 450 volts. Since a CRT is much larger it requires a much higher positive voltage in order to operate. A black and white TV might have a voltage from 7KV to 20KV depending on the size of the tube and a color TV (with its three electron guns) operates at anywhere from 20KV to 30KV. This high potential accelerates the electrons in a beam so that they can strike phosphorus on the screen which then emits the light you see. One problem, especially with older TV sets and early color sets is that if the current flowing through the tube is too high the picture tube (and other tubes relating to the generation and rectification of the high voltage) can emit X-rays. It is important to be able to measure the high voltage (in the KV range) present at the anode of a CRT in order to adjust the high voltage circuits to eliminate the chances of producing X-rays and also provide enough voltage for a bright focused picture.

How It Works:

The probe body is made of plastic that while clean and dry will not conduct electricity. The fins around the base act as a hand guard and also increase the surface area of the exterior of the probe so that a spark can only jump from one end of the probe to the other if the voltage is well in excess of 30K volts. Similar designs are used on glass insulators on telephone and antenna terminals to help dissipate the potential for lightning damage.

Inside the probe are two specially designed high-voltage / high-frequency resistors which are bolted together from end to end forming a path for electricity from the tip back to the base. These resistors are made of a carbon stripe which is deposited in a helix around a ceramic core. The value of the two resistors in series is 1090 megaohms. The entire resistor is then glazed over to seal it from moisture and insulate it electrically. Since the CRT anode voltage in a TV is pulsating at a rate of 15.624 kHz (for NTSC TV’s in the US) there is also some capacitive and inductive reactance which is accounted for in the resistors design.

The probe is designed to plug into the phono-jack style connector used on Heathkit meters of this period. The resistors inside the probe add to the overall impedance (resistance to alternating or pulsating current, i.e. A.C. Resistance) of the VTVM extending its own input impedance of 11 Mega-Ohms many times. This has the effect of adding a 100x multiplier when using the 300 Volt scale on the meter.

And More:

Since most modern electronics run on lower voltages and since CRT’s are becoming more and more rare in new electronic devices this probe is largely obsolete. However it is still useful for working on older TV’s and I have also used it in some high voltage experiments (along with a high-voltage Diode to rectify the alternating input source to D.C. before measuring.

You can learn more about Heathkit at the following links:

The Heathkit Virtual Museum:

Heathkit Schematics:

Manuals and Pictures of Heathkit Test Equipment:

A cool site about Vacuum Tube Volt Meters:

Thanks to everyone who took part (and especially to those who avoided taking part) in this weeks Identify It! Challenge.  Stay tuned for more Identify It!’s and feel free to contact us and share your own images related to science, technology, engineering, or mathematics that others can guess about and learn from.

Identify It! Answer for 5-27-2010

This week’s Identify It Challenge was guessed pretty quickly, and one fan even found a picture (until this post the only picture I know of this device on the internet today!) So great work everyone.  I took the liberty of obscuring the IBM logo on the original picture when it was posted in order to make it a little harder to look up the item. Here is the object without the IBM logo obscured.

The IBM Magnabelt Executary Model 224 dictation recording machine (1960s)

The IBM Magnabelt Executary Model 224 dictation recording machine (1960s)

This item is an IBM Magnabelt Dictation Machine (model number 224) also sometimes called an “executary”. IBM first introduced these machines in the early 1960’s. It was used to record dictation in the office and also as a method to record audio in the field by reporters. These machines are fully transistorized which lends to their smaller size and ability to be operated by battery. They did suffer from sound quality issues partly due to tracking problems with the recording belt, but also due to the poor quality of the included microphone. Today’s microphone technology is light years ahead of what was possible in 1960. In spite of these problems these units were a commercial success.

Magnabelt from another Angle

Magnabelt from another Angle

Closeup of the Microphone Connector, Proprietary Connector, and Microphone

Closeup of the Microphone Connector, Proprietary Connector, and Microphone

As you might know Thomas Edison invented the record player. He first marketed the record player as a business tool to record dictation. Early models used wax cylinders. As time went on other methods to record sound were devised including wire recorders and eventually tape recorders. The “executary” uses “magnabelt” technology where audio is recorded as a helical stripe along an endless magnetic recording belt. The belt is a mylar plastic belt with ferromagnetic material deposited on its recording surface.

Executary with leather carry case removed

Executary with leather carry case removed

The unit could be used in the field on battery power, or in the office connected to a base station via a proprietary power, audio, and control cable. For use in the field the unit had a thick leather carry case (which was the style at the time for portable electronic equipment like transistor radios). The leather case is held to the unit with a large captive thumbscrew. The picture above shows the unit with its leather case removed. Its exterior is a thin steel shell case with a flat gray paint job. The end piece is a black plastic.

Executary Case Slid Open

Executary Case Slid Open

To gain access to the magnabelt recording media or in order to adjust the recording level (a curious design limitation given there is a recording level meter in the operating controls) you can press a metal button on the back of the case and simultaneously pull the actual mechanism out of the case. There is a stop inside the case that keeps you from removing the entire case.

Recording Head lifted Open

Recording Head lifted Open

To get to the magnabelt you must first release a catch on the recording head mechanism and it swings open to about 25 degrees.

Magnabelt being removed

Magnabelt being removed

Closeup of Mechanism with belt removed

Closeup of Mechanism with belt removed

You can then gently lift up the portion of the belt that is pressed down by the recording mechanism and slip it off of its feed rollers. One benefit of the magnabelt over other kinds of tape (reel-to-reel, cassette, or cartridge types) is that it can be folded flat and sent through the mail to another person with another machine at normal postal expense, taking up much less space. One drawback to the technology though is that the physical alignment and tracking on a magnabelt is lost once it is removed or replaced, requiring the use of indexing and pitch controls.  Getting a totally accurate reproduction of the sound is more difficult.

Detail of Recording Head

Detail of Recording Head

The “executary” used a single head for recording and playback and does not include an erase head. Recording over used magnabelts would be possible but you would have to have used an external degaussing machine to scramble the magnetic domains on the tape to erase it first otherwise you would likely have had a mixture of old and new sound recorded. (especially if the belt had been removed and replaced… due to the tracking problem as mentioned above). The head is visible in the photograph above. The head is moved from left to right by a rotating threaded rod, this rod is geared to the motion of the magnabelt’s drive by a toothed belt. As the mangabelt moved below the head the head slowly moved to the left thus recording a helix around the belt. There is a tone/tracking adjustment wheel on the body of the recording mechanism (indicated with a tuning fork symbol). This adjustment moves the head slightly to the left or right in relation to the screw mechanism so that you can find the track if the belt is moved or if a belt from another machine is being played back.

Battery removed from the unit

Battery removed from the unit

The “executary” was powered by a proprietary 10.7 volt non-rechargeable battery that is marked with the IBM logo but manufactured for IBM by the Mallory corporation.

Typical use position

Typical use position

The unit was typically used by holding in the right hand and using the thumb to operate the controls. Inside the recessed blue square are the following controls and indicators: A tiny recording level meter, the power and playback volume control knob, the record button (which can be used as on/off or locked on for continuous recording), and a manual tape advance control lever that starts the tape moving for playback or recording. Also on the unit is the tone/tracking control, an indexing control that in some way marks the index strip of paper to indicate a start/stop/edit point and a manual release that disengages the tape head mechanism from its drive screw so that you can advance the listening/recording position on the tape. This is all relative from 0 to 100 on an index strip of paper that is held in place by friction inside the tape record head mechanism. This strip would be kept with the magnabelt if removed and used to label it.

Closeup of User Controls

Closeup of User Controls

In the later 1970’s advances in micro-cassette recording technology, integrated circuits, and better microphone technology replaced the “executary” style magnabelt recorders for office and portable use. Today micro-cassettes are still used but are largely being replaced by tape-less technologies such as recording directly to flash memory. In fact most cell phones have a recording capability for audio notes!

To learn more about the Magnabelt “Executary” and other older and proprietary audio recording technology check out this website:

Check back again in the future for more Identify It challenges and their answers.