The Relay

And it's effect on Technology

D Vautier
6/2023

Relays and Communication

A relay can be considered a way to magnify or project force.  It often applies to electronics but the term can also be used many other ways.  This discussion primarily focuses on its use in electronics but the magnification of force has been the basis of all modern social and technological advancement. You can set one switch and it causes many switches to react and do something bigger or more forceful.  So by setting just one switch a much larger and more powerful switch can be activated.  Thus it is a way to project or magnify power.  The dam operator can push a button and gigantic spillways open to release water.  An engineer pushes a button and an entire city goes dark.  A bombardier throws a switch and a bomb drops.

The very first relay

The first relay was the lever and people discovered it a long time ago.  It was used to move around big heavy things with less force, like big blocks for the pyramids.  Of course Archimedes came along way later and established the rules governing the lever but it was certainly in use a long time before 200 BCE.  As long as there was a stick or pole around you can make a lever out of it.  The bigger the stick the better the lever and the more force it can exert.  I’m sure that early humans knew how to take advantage of fulcrums and force vectors before they made any rules about it.

Telegraphy

With a better understanding of electricity, the age of electronic discovery began pell-mell about 1832 with the invention of the telegraph.  After that there was a huge inundation of inventions and contraptions involving this mysterious and occult science of electricity.  Communication became almost paramount and the world was breathtakingly caught up in a whirlwind of new inventions that came in rapid succession.

Samuel Morse and his code arrived on the scene just in time for the civil war, and 40 years later along came Alex Bell with his telephone and Tom Edison with his light bulb and phonograph, a huge bunch of achievements in a relatively short time.

In these rapid days of discovery, confusion often arises over who did what first but it was often more a case of who got to the patent office first.

Early Use of relays (or electronic levers or switches)

Lots of Morse’s little electric dots and dashes did not travel very far so they needed relays, or rather mechanical devices (like levers) that detected weak signals and re-transmitted them using stronger signals.  The way this worked was simple but involved often unreliable moving parts.  The incoming weak signal acted upon a coil which moved a switch and sent a stronger new signal out.  If all the relays worked as advertised than a signal got through.

Tools

Inventers soon developed a handbag of tools to work with this new field of electricity. They found out certain things could be done with electric voltage and current.  These assortment of tools could be used to play around with the electric signal like building blocks and gates and slides, hammers, and storage areas.

Copper wire allows electricity to flow normally but if a graphite filter is put in the way it slows the flow down.  This was called a resister.  If two large sheets of conductive material are very close together but not touching they tend to store electricity usually for a short time.  This device was called capacitor.  A device that allowed current flow just one way was called a diode.  So the toolkit increased including all kinds of stuff: coils, thermisters, variable capacitors, transducers, etc.

Transducers

A transducer is a device that converts an electric signal into mechanical energy or mechanical energy into an electric signal.  The electrical signal can be carried in different forms, like voltage strength or frequency change.  However the important thing with using an electric signal is that it's fast, like almost speed-of-light fast, and involves electrons, not mechanical relays, so it was quite important to be able to do this conversion from the mechanical to the electrical.

The key component of most transducers is a solenoid which consists of a coil of wire wrapped around a metal cylinder.  When electricity flows through a coil containing a piston, the piston moves back and forth according to the strength of the signal.  If the piston is attached to a big diaphragm you get a movement of air (a speaker).  If it is attached to a valve you get it to open or close a valve.  Working the other way, if the diaphragm is designed to be moved by sound waves, it drives a piston in a coil of wire which generates an electrical signal and you get a microphone.

The Telephone

In 1875 or thereabouts Alex Bell, along with many other curious minds I have to say, was close to solving the transducer problem which was really the golden fleece of electronics.  He built a device that could change the resistance of a small container of graphite powder through vibration.  He put an electric charge on one end of his container and by speaking into a cone directed at the container, his voice disturbed the graphite particles.  What came out of the other side of the little container was a variable voltage stream that happened to corresponded to the airwaves produced by his voice.  On the other end of these wires was a device which vibrated a diaphragm and produced airwaves that corresponded to his voice.

Of course there was the issue of distance.  After all no practical way existed to transmit the signal very far.  Also the wave pattern of a human voice is quite complex.  But with a lot of voltage it was able to work across town but that’s about all the farther the phone lines could go.  25 years later an answer arrived.

Vacuum tubes.

So how can a very weak complex electronic signal carrying the human voice get amplified so that it can travel over long distances by wire and not get lost?  The answer was the vacuum tube.  It was a pretty huge step in science because the device was able to accurately amplify complex electric signals.  This opened the door to the many possibilities and uses of electricity to carry actual sound by wire all over the world. 

A vacuum tube is just that, an airless glass container with a bunch of elements and filaments inside.  These elements can be complex and can have multiple uses but the basic tube consists of an anode, a grid and a cathode.  The cathode element gets hot and emits electrons in a vacuum.  The anode is positively charged and likes to absorb electrons.  However there is a grid in between these two elements which acts as a gatekeeper.  A small change in the grid charge produces a large change in flow from cathode to anode. This became a very accurate amplification of the original complex signal.

Wireless

In 1895, a dozen or so years after telephones were all the rage, Marconi invented a wireless way to send dots and dashes a few miles.  He did this by actually boiling photon packets off an antenna at a given frequency to create EMF.  The receiving device was set to accept the same frequency.  It worked and got better quickly.  Originally it was just able to send dots and dashes but soon evolved into radio which carried speech and music.

Transisters

A transistor is a solid state device that works very much like a vacuum tube.  It amplifies electrical signals. The current goes from the emitter to collector through the base. When the voltage in the base changes it effects the flow.  So small changes in base voltage cause large changes in the current and voltage flowing to the collector

In a way transistors were nothing more than a miniaturization of the vacuum tube.  But what was big, clumsy, hard to move, slow, delicate, hot and burned out easily became small, robust, durable, portable, very fast and did not require heat.  The best part was that the transistor fit nicely into the existing development of electrical science.

Computers

Some thoughts

The world has yet to catch up with all this technology which has far outstripped our social, behavioral, religious and political structures.  Within 150 years we have been subjected to so many overwhelming technological advances that it seems as though we just need to take a break and reflect on where it is leading us.