A(n) ? is a premises wiring system whose power is derived from a source of electric energy or equipment other than a service. Such systems have no direct connection from circuit conductors of one system to circuit conductors of another system, other than those established through bonding or grounding connections.

Separately derived system

Explanation: A separately derived system is used to describe a premise wiring system whose power is derived from a source of electrical energy such as transformer, solar photovoltaic cell or generator. A separately derived system has no direct connection to any conductor from another system or doesn't generate it's power from any direct connection to a conductor from another system or source except those from established from bonding or grounding connections. Separately derived systems usually generate it's power on it's own.

convex lenses are thicker at the middle. rays of light that pass through the lens are brought closer together (they converge). a convex lens is a converging lens. when parallel rays of light pass through a convex lens the refracted rays converge at one point called the principal focus.

scientific laws are the result of testing theories and proving them to be facts.