# What are single throw single pull switches and double throw double pull switches?

Discussion in 'General Electronics Chat' started by Infinity Series, Oct 21, 2014.

1. ### Infinity Series Thread Starter New Member

Oct 18, 2014
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Hi I am new to this site and currently learning about switches and circuits. I would like to know more about these switches and what kind of switches they are, also I'm currently attending a Introduction to Electronics class. In addition, would love to learn more from a professional in detail please. Thank you for your contribution. - Moses D

2. ### ScottWang Moderator

Aug 23, 2012
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single pole single throw - Just two pins for ON/OFF

single pole double throw - There are 3 pins, the pin 2 is the common pin, throw to left 1,2 pins On, 2,3 pins Open, throw to right 1,2 pins Open, 2,3 pins On,

double pole double throw - There are 6 pins and two sets of 3 pins independent switches, one of the switch that the pin 2 is the common pin, throw to left 1,2 pins On, 2,3 pins Open, throw to right 1,2 pins Open, 2,3 pins On, the other set is the same.

single pole single throw switch
single pole double throw switch
double pole double throw switch

3. ### djsfantasi AAC Fanatic!

Apr 11, 2010
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Here's a pic of a DPDT - double pole double throw - switch. Note that it is similar to two SPDT - single pole double throw - switches in parallel.

Last edited: Oct 21, 2014

Oct 15, 2009
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5. ### studiot AAC Fanatic!

Nov 9, 2007
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None of the replies so far, including the Wiki reference, actually describe the switches requested in the title of this thread, although they do contain useful information for beginners.

So here is some more terminology.

Switches provide a means of creating a connection or disconnection in electric circuits, and every switch has at least two positions it can be set to.
The original switch was a knife switch
http://en.wikipedia.org/wiki/Knife_switch
Which is easy to understand visually.

Although now basically obsolete, the terms 'pole' and 'throw' and 'throwing the switch' are derived from this type of switch.

Switches also have terminals that connect to the moving and fixed parts of the connection.

The term pole refers to the knife or moving part (moving terminal) of the connection.
The action of setting the switch to one of its positions makes or breaks connection between the moving terminal one or more of the fixed terminals.
Throwing the switch referred to setting the switch into one of its positions.
These days throw is often replaced by the word 'way', so we talk of a one way, two way, three way ...ten way switch rather than say a ten throw switch.

The simplest switch has at least two positions (on or off), but we don't count the off position.
So the throws or ways are the number of positions to which the switch may be set minus one

So an on/off switch is a single throw switch or a single way switch,
but it has two positions.
The on/off switch has one moving and one fixed terminal.

The next simplest switch is a two way or double throw switch which can connect the moving terminal to two different circuits or two different parts of the same circuit.

Note you can always make use a switch with more ways by simply not connecting some of the ways to anything.

Now as djsfantasi noted in his post#3 you can run two switches side by side in parallel, and he has provided a useful diagram showing this.
However that can be inconvenient, especially if you have lots of switches to set.

If, however we mechanically 'gang' the switches to operate from a single mechanism we can set two or more switches in one single action.

The 'ganging' is shown as a dashed brown line in fantasi's diagram.
Ganging is also used for other components such as variable resistors, capacitors etc.

Furthermore the ganged switches do not have to actually be in parallel (which is a particualr electrical term) or even in the same circuit, they just need to be operated together for some reason.

The number of gangs is the number of electrically indpendent switches which is the number of poles or moving terminals in the switch.

So a double gang switch = a double pole switch.

A double pole on/off switch = a double pole single throw or double pole single way switch.

and so on.

ScottWang has given you a bit of a longer list showing the abbreviations.

Now back to the mechanical actuation or operation of the switch for the last part of your question.

The Wiki article has lots of mechanical means to operate the switch, levers, shafts, buttons, rockers etc and all of these can be used in the description of the switch
So, for instance, you operate a rotary switch via a shaft and so on.

Also the Wiki article describes the action of the mechanism as latching, make before break, momentary etc

The pull switch is a special purpose switch designed to be operated by pulling on a pull-string or pull-cord.
They are usually self latching.
You might find the single pole variety dangling under an electric wall light or other appliance mounted to high to reach.
These will be latching on/off types.
Because pull switches provide particularly good insulation they are mandatory in UK bathrooms and the double pole variety can be found switching both line and neutral feeds to an electric shower.

Does this help?

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6. ### mcgyvr AAC Fanatic!

Oct 15, 2009
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I just assumed "pull" was a typo and that "pole" is what they actually meant.

7. ### studiot AAC Fanatic!

Nov 9, 2007
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Yes they are similar words and that was my first reaction too.

8. ### gerty AAC Fanatic!

Aug 30, 2007
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That's the way I read it also

9. ### djsfantasi AAC Fanatic!

Apr 11, 2010
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Since it was used in the context of single pull and double pull, I also read it that way.

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