Signal Management Flashcards
What is the difference between a Wire and a Cable?
A wire contains only one conductor, either a solid or stranded material, covered by an insulating sleeve.
A cable is a number of wires running parallel together, each individually insulated.
The cable may or may not be separately protected by an outer shield and/or jacket.
How would the conductors in a wire or cable be described or classified?
Conductors are predominantly described by:
Material (eg copper)
Construction (ie solid or stranded)
Size
What are the comparative advantages of solid and stranded conductors?
Solid conductors tend to be stronger than stranded equivalents, but are harder to bend and handle. Easier to manufacture, they would normally be cheaper than stranded.
Stranded cables consist of multiple thin strands, making the cable more flexible, but also more expensive, slightly thicker and less robust.
What is flex life?
Flex life describes a cable’s resilience to constant movement, such as in a live event situation where cables are continuously set up and torn down.
What is an insulator?
A insulator is designed to prevent two conductive materials from coming into contact and preventing the passing of current from one to the other.
What is dielectric constant?
Dielectric constant is the ability of an insulator to prevent the flow of electricity between two conductive materials.
For accuracy, the term dielectric constant is now being replaced by Relative Permittivity.
Why do some cables have an additional outer shield?
Cables can be specified with a shield which is designed to isolate the wires from electromagnetic and radio interference.
Name three types of shield?
Foil sheild
Braided shield
Combination shield
What is a Drain or Ground Wire?
A Drain wire is a bare wire which runs inside a foil shield, allowing the shield to be terminated at each end.
What is a cable jacket?
The jacket is the outer layer of the cable that protects all of the inner cores.
Why are cables with polyethylene jackets never used indoors?
Polyethylene is relatively inexpensive, but highly flammable, and therefore unsuitable for installation internally.
Name a common material used for cable jackets that is suitable for use within buildings.
Teflon is designed to resist fire and works well indoors, but is more expensive than other materials.
What is a coaxial cable (coax)?
Coaxial cable is an unbalanced cable, often used for short runs of video signals. There is usually a central insulated wire sheathed by an outer stranded layer. The central wire is usually the conductor with the outer shield acting as the return. Both conductors share the same axis, hence the name.
What is the advantage of using Twisted Pair cables?
Twisted pair cables involve two individually insulated wires twisted around each other all along the length of the cable. The two cables are each exposed to the same interference, and by using balanced circuitry this interference can be removed.
Category 5 cable, for instance, has 8 separate wires (4 twisted pairs) surrounded by an outer foil and drain wire.
What are the advantages of using fibre optic cables?
If digital signals are either on or off, then instead of an electrical current, optical fibre allows the transmission of light instead, with the light either on or off. The major advantage with sending light is that is is much less susceptible to external interference.
What are the two main types of optical fibre?
Single mode or multi mode.
What is an XLR connector?
An XLR connector is a push and lock pin connector.
It can be provided in 3 pin to 7 pin configurations.
3 pin XLRs are common for microphones, while 5 pins are the standard for digital lighting applications and many stereo headsets.