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Fail-safe and fail-secure are distinct concepts. Fail-safe means that a device will not endanger lives or property when it fails. Fail-secure, also called fail-closed, means that access or data will not fall into the wrong hands in a security failure. Sometimes the approaches suggest opposite solutions.
At the server level, failover automation usually uses a "heartbeat" system that connects two servers, either through using a separate cable (for example, RS-232 serial ports/cable) or a network connection. In the most common design, as long as a regular "pulse" or "heartbeat" continues between the main server and the second server, the second ...
A collection of computers and other devices connected by communications channels, e.g. by Ethernet or wireless networking. network interface controller. Also LAN card or network card. [6] network on a chip (NOC) A computer network on a single semiconductor chip, connecting processing elements, fixed-function hardware, or even memories and caches.
Generically, an NID may also be called a network interface unit (NIU), [1] telephone network interface (TNI), system network interface (SNI), or telephone network box. Australia's National Broadband Network uses the term network termination device or NTD. A smartjack is a type of NID with capabilities beyond simple electrical connection, such ...
A part failure mode is the way in which a component failed "functionally" on the component level. Often a part has only a few failure modes. For example, a relay may fail to open or close contacts on demand. The failure mechanism that caused this can be of many different kinds, and often multiple factors play a role at the same time.
In semiconductor devices, problems in the device package may cause failures due to contamination, mechanical stress of the device, or open or short circuits. Failures most commonly occur near the beginning and near the ending of the lifetime of the parts, resulting in the bathtub curve graph of failure rates.
A system designed to experience graceful degradation, or to fail soft (used in computing, similar to "fail safe" [13]) operates at a reduced level of performance after some component fails. For example, if grid power fails, a building may operate lighting at reduced levels or elevators at reduced speeds.
In a similar vein, an industrial or domestic burner controller can fail, but must fail in a safe mode (i.e. turn combustion off when they detect faults). Famously, nuclear weapon systems that launch-on-command are fail-safe, because if the communications systems fail, launch cannot be commanded. Railway signaling is designed to be fail-safe.