# Need help to understand DigiKey/Mouser “Switch Function” terminology

I first read Switch Basics from Spark-Fun tutorial to help me better understand how to find what I am looking for using DigiKey/Mouser Advanced search terminology.

I know I am looking for a maintained latching switch where I push once to turn on, push again to turn off.

When I look at the DigiKey/Mouser advanced search under the "Switch Function" section I find:

DigiKey:

• Off-Mom
• Off-Mom-Mom
• On-Mom
• Mom-On-Off
• Off-On: Does this mean that the switch is initially off? Then it is on when pushed?
• On-Off: Does this mean initially On?
• On-Off, Off-On: Is this a toggle type?
• On-On-On-Off

Mouser:

• (ON) - (OFF)
• OFF - (ON)
• ON - (OFF)
• ON - OFF

What is the difference between each function?

• Why are you shopping for components on e-bay? Check a real distributor, like Mouser. – Samuel Feb 3 '15 at 21:15
• Thanks @Samuel, what you found is fantastic. I initially tired, but I got lost into terminology. What switch function did you search by? – lucidgold Feb 3 '15 at 21:30
• The terminology isn't consistent. That switch is the only in-stock one in the "(ON) - (OFF)" category (the parenthesis apparently denoting a stable position). It's also called a "double-action" switch. Or "Snap action/Push-on type SPDT". The 'latching' term is used by relays, so will usually be saturated with erroneous results. In the future to avoid closure, your question should be about terminology, rather than the product. I would think that will hold up anyway. – Samuel Feb 3 '15 at 21:37
• Thanks again @Samuel, I have made a few more fixes to my question. Hopefully it is now more useful. Also thank you for clarifying some of the terminology! I will update my post! – lucidgold Feb 3 '15 at 21:41
• On digikey at least it is usually the first one is what it starts as, the second is what it is when depressed. So on-off is on normally and off when depressed. And if it says mom it means it is momentary and not latching. Mouser uses parentheses to indicate momentary switches I think. If it has a comma between two types like on-off, off-on it might be a double pole switch where one pole is normally on and the other is normally off. (NO is usually normally open so don't let that confuse you if you see it on datasheets, open=off) – I. Wolfe Feb 3 '15 at 21:44

Digikey:

Off-Mom         = Continuous OFF momentary ON SPST
Off-Mom-Mom     = Continuous OFF two momentary ONs SPDT
On-Mom          = Continuous ON momentary SPST
Mom-On-Off      = Momentary ON continuous ON and continupus OFF SPDT
Off-On:         = Toggle ON/OFF SPST
On-Off: Toggle  = ON/OFF SPST
On-Off, Off-On: = Toggle ON/OFF DPST inverted poles
On-On-On-Off    = Three continuous ON positions, one continuous OFF position SPTT


Mouser:

(ON) - (OFF) = Momentary both ways
OFF - (ON)   = Momentary ON
ON - (OFF)   = Momentary OFF
ON - OFF     = Toggle