daisy chain

Daisy chain

Daisy chain

A daisy chain, in the most elementary sense, is a garland created from the daisy flower, generally as a children's game. The words "daisy chain", or "daisy chaining" also have a number of technical and social meanings (some given below), which likely stemmed from this pursuit.

Flowers

One method of creating a daisy chain is as follows: Daisies are picked and a hole is made towards the base of the stem, generally by piercing with fingernails. The stem of the next flower can be threaded through until stopped by the head of the flower. By repeating this with many daisies, it is possible to build up long chains and to form them into simple bracelets and necklaces.

There is another popular method which involves pressing the flower heads against each other, so that the final chain looks like a caterpillar.

Electrical and electronic engineering

In electrical and electronic engineering a daisy chain is a wiring scheme in which, for example, device A is wired to device B, device B is wired to device C, device C is wired to device D, et cetera. Connections do not form webs (in the preceding example, device C cannot be directly connected to device A), nor do they loop back from the last device to the first. Daisy chains may be used for power, analog signals, digital data, or a combination thereof.

Physical arrangement

In popular usage, the term sometimes merely describes the layout of physical connections. For example, in a daisy chain of power strips, while the power strips are physically plugged into each other in a chain, any devices that receive power from the chain are electrically connected in series;not in parallel (see series and parallel circuits). Additionally, a daisy chain may be an arrangement in which a daisy chain wiring pattern is in use even though neither the standard nor the physical devices in use mandate that wiring pattern. In particular, tree-based systems such as USB, FireWire, and modern ethernet can be wired in a daisy chain if desired. A notable exception, thin ethernet is usually physically arranged as a daisy chain of T-connectors on network cards, but is almost never referred to as one.

Signal transmission

For analog signals, connections usually comprise a simple electrical bus and, especially in the case of a chain of many devices, may require the use one or more repeaters or amplifiers within the chain to counteract natural attenuation. Digital signals between devices may also comprise a simple electrical bus, in which case a bus terminator may be needed on the last device in the chain. However, unlike analog signals, because digital signals are discrete, they may also be electrically regenerated, but not modified, by any device in the chain.

SCSI

SCSI is an example of a system that is electrically a bus but, in the case of external devices, is physically wired as a daisy chain. Since the network is electrically a bus, it must be terminated and this may be done either by plugging a terminator into the last device or selecting an option to make the device terminate internally.

MIDI

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MIDI devices are usually designed to be wired in a daisy chain. It is normal for a device to have both an OUT port and a THRU port and often both can be used for chaining. The OUT port gives a completely regenerated signal and may add, remove, or change messages, but introduces some delay in doing so. The THRU port provides a minimally delayed (only electrical amplification and opto-isolation) copy of the signal but suffers from asymmetry due to the opto-isolator distorting the signal with each item in the chain. If the chain is long enough, it will be distorted so much that the system will become unreliable or completely non-functional. Due to the above issues with both types of chaining, a variety of MIDI devices that take one input and split it to many outputs have appeared on the market.

SPI

Some Serial Peripheral Interface Bus IC products are designed with daisy chain capability.

Information technology

Computer software

The term is also used in computer software. Daisy chain installation is a "smart" installation, whereby an installation can happen piecemeal, as all the components of the package are connected to each other. If there is a disconnect during a web-based installation the software need not be downloaded from scratch, but rather restarted from where it stopped. Eg: the installation of Google Pack.

Computer hardware

The term is also used when connecting multiple hardware using the same communication protocol to a shared communication bus. For example when you connect multiple hardware having UART ports which communicate via RS-232 protocol to the same physical bus, you are making a daisy chain. This means that you wire all RX signals together and all TX signals together and so on. Then a predefined logic would allow only one of them to seize the bus in a given time. This way you say that your devices are daisy chained. Some other situations or protocols which use daisy chains are SCSI and Firewire devices.

System access

The term is also used in the context of the Session-, Application- or Presentation Layer when a computer system is not being accessed directly but rather by deliberately hopping via other systems first. In the easiest example, a telnet or SSH connection is established from the first machine to the shell on a second machine, and then from the second machine to the shell on a third machine. Another typical example is the "terminal session inside a terminal session" using RDP. There are many reasons to create such types of daisy chains, such as to connect to a system on a non-routed network via one or more gateway systems, keeping sessions alive on a main computer while not being connected to this main computer at all times, to save bandwidth or when on an unstable network by first connecting to a better connected machine, or even in an attempt to cover ones tracks while engaged in cybercrime.

Type of knot

In many applications of rope work (i.e. canoeing/boating), rope may be stored by tying it into what is referred to as a daisy chain (see daisy chain (knot)). This is accomplished by the same process that backpackers use, only for a storage purpose instead of utility. A loop is pulled through the rope on the first link, then the process is repeated for the length of the rope. At the last link, a half hitch is tied to stop the rope from coming undone. To undo the daisy chain, simply undo the half hitch and pull - the knot will slip apart.^[1]

Rock climbing

In rock climbing a daisy chain is a strap, several feet long and typically constructed from one-inch tubular nylon webbing of the same type used in lengthening straps between anchor-points and the main rope. The webbing is bar-tacked (sewn) across at roughly two inch intervals (or, in the past, tied) to create a length of small loops for attachment. Unlike the use of similar devices in backpacking, daisy chains in technical rock climbing are expected to be of sufficient strength to be "load bearing," i.e., capable of withstanding forces sustained by the anchor system in a fall.

Though daisy chains are sometimes used by free climbers as a type of chicken sling (a quick attachment used from harness directly to a belay anchor), and for ad hoc purposes similar to those of the backpacker, the canonic use for a daisy chain is in aid climbing, wherein the leader will typically attach one end to the harness, and the other to the top-most anchor placement (by carabiner or fifi hook), particularly after having ascended in etriers as high as possible. This allows the leader to hang from the daisy chain while preparing the next anchor placement. The closely spaced loops allow fine-tuning the length from harness to anchor, thereby allowing the best possible reach for the next placement.

Daisy chains should not be confused with etriers (aka aiders) which are short ladders made in the same way, but with larger loops, also used in aid climbing, nor with load-limiting devices often known as screamers (from their first trade name) designed to simulate a dynamic belay.

Backpacking

A daisy chain in backpacking is a small strip of webbing with multiple loops, which allows the backpacker to secure many different types of objects to the exterior of the pack.

Recreational fishing

A "daisy chain" is often used in recreational troll fishing. This is a "chain" of plastic lures, however they do not have hooks- their main purpose is to merely attract a school of fish closer to the lures with hooks.^[2]

Typically, the main line of the daisy chain is clear monofilament line with crimped on droppers that connect the lure to the main line. The last lure can be rigged with a hook or unrigged. The unrigged versions are used as teasers while the hooked versions are connected to a rod and reel. The lures used on a daisy chain are made from cedar plugs, plastic squids, jets, and other soft and/or hard plastic lures.

Military

A daisy chain is used in military terms to describe how individual units of exploding ordnance, (Claymore mines, C-4 explosives, and IEDs), are linked together. These units are linked together in a pattern of any design in order to create a wider area of damage that would explode at generally the same time. It was also used by a group of paratroopers who exited an aircraft with only the last having his static line attached. All the other jumpers' static line were attached to the man behind him. Therefore, all the jumpers were in a freefall until the last man's static line was pulled.

Also used to describe the way oxygen hoods can be linked together to an oxygen source on a submarine during a drill, fire or something else where air supply is a problem.

Relationships

A daisy chain also refers to any series of complicated relationships in which, over time, people have had different partners who have themselves had other partners within the same group of people.

Human sexual relations

A daisy chain refers to sexual relations among three or more people, with each person both performing and receiving oral sex simultaneously.^[3] Some sources consider only groups of five or more people to be a daisy chain.^[4] Though the practice is thought to be gaining popularity among teenagers, there are doubts about how widespread the phenomenon actually is.^[5][6]

References

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