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On Thursday, August 21, 2003, at 2:45pm, my wife of 34 years, Rebecca, died in my arms in an emergency room.

The last words we spoke were in perfect synchronization: "I love you with all my heart."


Understanding Switches


If you work on Hammonds or Leslies, it's very important to really understand switches.


This page might be very helpful for beginners, and very boring for those that already know about switches.


Everywhere in your life are switches.  They are made in hundreds of shapes, types, and configurations - for all kinds of different purposes. 

But the one thing ALL switches have in common is this: they either MAKE or BREAK a connection.


Let's think simple, and we'll get more detailed as we go along.  First, let's think about a light switch - just like the ones in your house.

If we had x-ray vision, we could see the switch has TWO wires connected. 


One wire (hot) comes from your house wiring.  Directly, or maybe not so directly, it brings voltage from your breaker box - connected to your local electric company. 

Typically, (regarding electric code), it brings (hot) 110VAC INTO the light switch. 

If you touch this wire, AND you touch an electrical common or ground, YOU WILL BE SHOCKED. 

You might be knocked to the floor!


The light switch has a second wire, too.  It ends up at your light fixture.

This switch is known (electrically) as a SPST (single pole, single throw) switch. 

Turning the switch ON electrically CONNECTS that "IN" (hot) wire (from the breaker box) to the "OUT" wire (your light fixture) and the light bulb illuminates.

Turning the switch OFF electrically DISCONNECTS that "IN" (hot) wire (from the breaker box) to the "OUT" wire (your light fixture) and the light turns off.

Try to remember .... voltage IN and voltage OUTMAKE or BREAK a connection.


But that's not the end of it.  Your light (and any electrical device) requires a second (common or neutral) connection. 

Look at one of your wall outlets, for example. 

You should see THREE openings there: one for GROUND, one for COMMON, and one for HOT. 


Ground is required for various applications, but not required for others. 

Look at your cell phone charger: no ground pin - it's not needed.  Look at a lamp plug: no ground pin - it's not needed.


OK - I hope we now understand the concept of SPST switches.  More important, I hope we understand that VOLTAGE requires TWO conductors.

Typically, 110VAC requires a black (hot) and a white (common or neutral) connection. 


DC voltage is similar, requiring POSITIVE and NEGATIVE conductors.  With DC voltage, the negative side is considered "ground".

Look at an ordinary AA battery - one end is positive (+), the other end is negative (-).


What if you wanted to control TWO, SEPARATE devices with ONE switch?  Let's imagine this: a 110VAC amplifier, and a 12VDC car stereo.

That's easy!  A DPST (double pole, single throw) switch is the answer.  One side switches 110VAC, the other side switches 12VDC.


We aren't done yet.


Imagine a switch that did ONE job in ONE position, and a DIFFERENT job in the OTHER position.  The switch is known as a SPDT (single pole, double throw). 


So - let's imagine again.

You have ONE switch - it's a SPDT switch.  You have a RED light connected to one side of the switch, and a BLUE light connected to the other side.

As soon as you wire this and provide power, one of the lights will be ON.  Flip the switch, and the first light turns OFF, while the other turns ON.


BUT!  There's another option: it's known as "CENTER OFF".  With this type switch, you now have THREE switch positions - one lights the BLUE light, center position is OFF, and the other position lights the RED light. 


We still aren't done.


There is another type switch which is normally (via an internal spring) in the OFF position.  Pushing the switch enables an electrical circuit, and releasing the switch stops the electrical flow.  Examples?  Your computer keyboard.  The ignition/start switch in your car.  And the car horn, too.  These type switches are referred to as MOMENTARY CONTACT (MC) switches.


Vintage Hammond console organs have amazing switching in the manuals. 

Each key controls a 9PST (9 pole, single throw) switch .... and there are 61 playing keys on each manual! 

Pressing down a key actually closes 9 individual pairs of contacts.  Look at some pictures of all that wiring. 


There's a lot more.  There are so many types of switches, I could write about them for 10 years.

When I have time, maybe I'll add to this page.


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