# Switches: Difference between On-OFF-On and On-NONE-On?



## Edwood

Was shopping around for SPDT switches, and noticed there were On-OFF-On and On-NONE-On versions? What is the difference between the two? 

 -Ed


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## Sovkiller

Quote:


  Originally Posted by *Edwood* 
_Was shopping around for SPDT switches, and noticed there were On-OFF-On and On-NONE-On versions? What is the difference between the two? 

 -Ed_

 

IMO they are basically the same, maybe different manufaturers call them in different ways...if there is any other difference I would like ot know also...


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## seiko_citizen

Excuse my n00b! What is SPDT? and the diference between them and other switches


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## Edwood

Quote:


  Originally Posted by *Sovkiller* 
_IMO they are basically the same, maybe different manufaturers call them in different ways...if there is any other difference I would like ot know also... 
	

	
	
		
		

		
		
	


	


_

 

This is what confuses me, manufacturer's offer both versions.

 I suspect On-NONE-On means the ground is switched off as well, while On-OFF-On leaves the ground connected? 

 -Ed


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## PinkFloyd

Quote:


  Originally Posted by *seiko_citizen* 
_What is SPDT?_

 

Single Pole Double Throw


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## Alick

Quote:


 What is SPDT? 
 

Single Pole Double Throw. It's a single channel change-over switch. DPDT is more commonly used for switching two supply lines or two stereo channels simultaneously. 

 On-Off-On has a centre position where the common pole is not connected to either of the other two poles. I'd guess that On-None-On is a different way of saying the same thing. The other option is the simple changeover where the common pole is always connected to one or other of the other two poles.

 EDIT: Mike beat me to it...


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## seiko_citizen

SPDT - is just an ON-OFF.
 DPDT - similar to a rotary switch correct?


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## Alick

Quote:


 SPDT - is just an ON-OFF.
 DPDT - similar to a rotary switch correct? 
 

Sorry, but both statements are wrong. The first two letters indicate the number of poles (lines) which can be switched simultaneously: SP (single pole) = 1, DP (double pole) = 2, etc. The second two letters indicate the number of "throws" or alternative connections which can be made. ST (single throw) can make/break one connection (ie, on or off). DT (double throw) can alternate (changeover) between two connections (ie, the common pole can be connected to one of two other poles). 

 A relatively easy way do distinguish between them is to count the poles on the back of the switch: two poles - SPST, four poles - DPST (these are both on/off), three poles (SPDT), six poles (DPDT) (these are both changeover switches). Double throw switches can have a centre-off postion (on-off-on), but not all do.


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## Syzygies

Download and study the datasheet http://www.nkkswitches.com/pdf/M2toggles.pdf, for a representative family of toggle switches. Staring at this datasheet is nearly as good as taking a bunch of toggles apart and testing them. Downloading a bunch of these sheets is nearly as good as getting lost in a hardware store.

 They don't explain all terms, but there is only one consistent explanation for their use of language. In particular, toggles generally break one connection before making another ("break-before-make" or "non-shorting"; one needs "shorting" rotary switches e.g. for making stepped attenuators). "On-Off-On" indicates the switch can rest in a middle position between connections; "On-None-On" indicates there are only two rest positions, making one connection or the other. "On-None-(On)" means one of these positions is actually momentary.


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## gsferrari

On-Off-On : Discrete middle position
 On-None-On : Transient middle position

 With a double-throw switch, ON - NONE - ON means it's a two position switch - pushed one direction, one set of poles is connected to the center poles. Pushed the other direction, the other set of poles is connected to the center poles. ON - OFF - ON adds a center position where nothing is connected to the center poles. This is good for some applications but not really worth much here


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## Okkler

Thanks for all the great info on switches. That really cleared up some stuff Ive been wondering myself. Do you need to ground a switch for it to work properly? If so, how do you go about doing this?


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## dip16amp

Quote:


  Originally Posted by *Edwood* 
_Was shopping around for SPDT switches, and noticed there were On-OFF-On and On-NONE-On versions? What is the difference between the two? 

 -Ed_

 

The difference between the NKK M2112 On-None-On and the M2113 On-Off-On SPDT switches is the LED illumination when in the center position. The On-None-On has no LED connection in the no center position while the On-Off-On will in the center off position.


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## gsferrari

Quote:


  Originally Posted by *Okkler* 
_Thanks for all the great info on switches. That really cleared up some stuff Ive been wondering myself. Do you need to ground a switch for it to work properly? If so, how do you go about doing this?_

 

Depends on what you intend to do. A simple On-Off switch does not need a ground...just cut off the negative terminal via the switch. If this is a switch for comparing sources, amplifiers or headphones - then you will need grounding and you will have to watch the grounding scheme closely to avoid ground loops and other problems...


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## shippreck

I did not see Syzygies answer. That explains it.


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