High-frequency direction findingHigh-frequency direction finding, usually known by its abbreviation HF/DF or nickname huff-duff, is a type of radio direction finder (RDF) introduced in World War II. High frequency (HF) refers to a radio band that can effectively communicate over long distances; for example, between U-boats and their land-based headquarters. HF/DF was primarily used to catch enemy radios while they transmitted, although it was also used to locate friendly aircraft as a navigation aid.
Civil codeA civil code is a codification of private law relating to property, family, and obligations. A jurisdiction that has a civil code generally also has a code of civil procedure. In some jurisdictions with a civil code, a number of the core areas of private law that would otherwise typically be codified in a civil code may instead be codified in a commercial code. The history of codification dates back to ancient Babylon. The earliest surviving civil code is the Code of Ur-Nammu, written around 2100–2050 BC.
BridgeA bridge is a structure built to span a physical obstacle (such as a body of water, valley, road, or railway) without blocking the way underneath. It is constructed for the purpose of providing passage over the obstacle, which is usually something that is otherwise difficult or impossible to cross. There are many different designs of bridges, each serving a particular purpose and applicable to different situations.
