Note Randy's pic of the Perkins pushbutton switch: Now that's a knife-blade contact, is it not? You don't see that nowadays, ever, on a snap switch. Think for a minute about why they are called "snap switches".
Nowadays, they just don't "snap" the way they used to. I remember 25 years ago, the manufacturers made a virtue of this: the "silent" light switch! (And I can remember professional curmudgeon Andy Rooney ridiculing the claim: "We have stereos that blare for blocks around, and we have 'silent' light switches!")
The reason for the loud "snap" is the very stout spring used to make and break the contacts. 100+ years ago when these switches were designed, the standard service equipment was a knife switch, and electricians practiced the habit of opening and closing them quickly to minimize the arc. It was judged that the average non-technical person could not be trusted to do this properly, so the spring (not to mention dead-front construction) was added.
Why all the fuss? Two letters: DC. 110V DC service was common in urban areas, and remained so until the middle of the 20th century. These old "snap" switches could take the brutal DC arc and keep going. Feed them AC, and they can go for 100+ years.
It's funny my memory of things electrical only goes back 25 years, when I would go to the hardware store with my dad, and guess which aisle I'd end up in? But they had a lot of stuff that I guess was archaic even then. The old DC-rated switches hung on longer than DC service did. In latter days, they were called "T-rated" (as in tungsten).
Oh yeah, and those surface-mount rotary switches? Go to the ConEd Pearl Street museum in NYC. Edison invented those.
[This message has been edited by yaktx (edited 11-02-2006).]
