Q: I'm looking at some control panel specifications, and some of the relays are designated "Form A" while others are designated "Form C." What are these forms, and is there a single relay that meets both criteria?

A: Form letters are part of an ANSI standard that defines the arrangement of contacts for relays and switches. The three most common types in our industry are Forms A, B, and C, and here's how they translate: Form A means single pole, single throw, normally open (SPST-NO). Form B means single pole, single throw, normally closed (SPST-NC). Form C is single pole, double throw (SPDT). Since Form C contacts can be wired for either normally open or normally closed operation, you can probably build your panel using all Form C (SPDT) relays. In small sizes, the added cost of the second contact is insignificant. As current ratings go up, though, you'll want to be more selective. There are many other standard forms (they go to Form Z and beyond). Call your Kele Sales Associate for assistance if you run across a strange one!