DPDT
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A Double-Pole Double-Throw (DPDT) or changeover switch is one that has two electrically independent but mechanically linked sets of contacts ("double pole") where each pole has contacts at both switch positions ("double throw").
DPDT can also refer to a relay where it means exactly the same thing except that the contacts are operated by an electromagnet instead of a mechanical level or button.
It is also possible to have more than two sets of contacts in the same package. They can be indicated by 3PDT or 4PDT, where the number indicates the number of poles.