Closed circuit means a complete electrical connection around which current flows or circulates.(noun)
When you have a series of electrical wires connecting to each other and completing a circuit so that current travels from one end of the circle to the other, this is an example of a closed circuit.
The definition of closed circuit is a system where video or other media is transmitted through connected cables and wires, not through the air.(adjective)
When you have a video camera directly connected to a TV on the property that shows images from the video camera, this is an example of a closed-circuit TV.
See closed circuit in Webster's New World College Dictionary
See closed circuit in American Heritage Dictionary 4
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