switch on a switch?

[CheckItOut]

1965 house... One wall switch appeared to do nothing and I thought the overhead bulb may be gone. Switch on the opposite side of the room turned on said overhead bulb. Once on, the "dead" switch worked just fine. So, if the "master" switch is on, the other switch works. Is this a switched switch and what for?

[Bill Kibbel]

A switch was probably replaced on a 3-way with the wrong type and/or incorrectly wired.

It just takes a minute or two to pull the switch plates to confirm.

[Chad Fabry]

I had a brand new three way switch that was open in one position. I was almost at the point of tearing down wall board to figure out what the problem was.

[Home Pride]

I see miswired 3 way circuits frequently.

[Bain]

Me, too. Lots of times people will replace a three-way toggle switch with a regular dimmer switch.

That drawing, Bill, is splendid. Much better than the diagrams that typically come with three-way installation instructions.