On-Off-On vs. On-None-On .

I'm looking at the Mouser Electronics catalog, at DT rocker switches, and I'm wondering what the difference is between

On-Off-On and On-None-On .

The second is used much less, but, suprisingly, it's used in the same section, from the same maker, as the first is used.

A guy on the web says ""On-None-On" indicates there are only two rest positions, making one connection or the other. " but again, the same maker will have many other DT swtiches marked On-Off, so that's a little hard to believe. Or is that false too, and None means the middle position of the switch is not connected to the neon light in the switch, but Off just means the other loads aren't connected?

I'm also wondering if there is a difference between

On-Off-(On) and On-Off-Mom ?

Is the second a new category for Mother's day? That's today, but I'm pretty sure this catalog was printed years ago, since i've had it for years. And again, Mom is used much less, but when it is used, it's the same maker and the same section where (On) is used.

If one maker uses both terms, it seems like, in both cases here, they might have different meanings, but I can't think of any.

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Mom is spring return.

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I raised this issue sometime last year. The terminology can be confusing.

ON-OFF-ON means the switch has three positions. In the center position, none of the contacts is closed.

An ON-(none)-ON switch is a regular DPDT switch. It has no central third position.

Does this make sense?

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William Sommerwerck


** "On-Off " indicates the switch has two contacts ( per pole) instead of three.

.... Phil

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Phil Allison


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seem to


I suspect that really crappy translations are the primary cause of these weirdness.


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No, these are from American catalogs selling (mostly) American-made switches. "Someone" decided to change the way multi-throw switches are labeled/designated.

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William Sommerwerck
[mom] is momentary. it returns to [off] once you let go. on-off can be make-before-break, which is sometimes super useful, sometimes super sketchy. on-none-on clarifies that the switch is definitely break-before-make. It only has two positions. on-off-on is as previously mentioned. not sure myself about the use of brackets; eg off-(on) versus off-on Methinks it could be [mom] notation
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