Cable Fundamentals

1. Cable Fundamentals

2. Code A rule intended to ensure safety during installation, use, andlor disposal. Typically invoked and enforced through governmental bodies • Standard Guideline documentation that reflects agreements on products, practices, or operations by nationally or internationally recognized industrial, professional, trade associations, or governmental bodies • Regulation Usually issued by governmental agencies and considered a mandatory rule In the US, a typical agency that issues regulations is the FCC Codes and Standards

3. Standards and codes contain two key words Shall—mandatory requirement Should—advisory recommendation

4. Codes address the safety of persons, property, and the environment associated with cabling installation They include • Electrical codes • Building codes • Fire codes • Environmental codes • Safety codes When adopted by the AHJ, codes have the force of law

5. National Electrical Code (NEC) • Published by National Fire Protection Association • Sets minimum standards to protect people and property from electrical hazards • Used by most federal, state, and local governments • Some states and localities adept more stringent requirements • Revised every three years

6. Standards establish a basis to compare, measure, or judge • Capacity • Quantity • Value • Quality • Performance • Limits • These may be different in other systems, but the majority of the time its similar

7. The movement of information as electrical or optical signals • The use of copper conductors and glass strands for the passing of signal in either analog or digital form Transmission of signal

8. Mhzvs Megabit • Mhz Information-handling capability of the media (The size of the highway) • Megabits Transmission rate Number of bits of information that can be transported over the media (Vehicles on the highway)

9. Frequency • Frequency is defined as the number of cycles a signal is repeated in a given time period. • Typically, an ac signal is shown as a sine wave. If the unit of time is equal to I second (s), the frequency is stated in hertz (Hz).

10. The following are frequency unit sizes and names: • 1 cycle in 1 second= 1Hz • 60 cycles in 1 second = 60 Hz • 1000 cycles in 1 second = 1 kHz (kilohertz) • 1 million (1,000,000) cycles in 1 second = 1 MHz (megahertz) • 1 billion (1,000,000,000) cycles in 1 second = 1 GHz (gigahertz) • 1 trillion (1,000,000,000,000) cycles in I second = I THz (terahertz)

11. Bandwidth • Bandwidth is the information-carrying capacity of a system. The end-to-end bandwidth of • a system is related to the respective bandwidths of its component parts. • The bandwidth or capacity of a system will also vary depending on its length.

12. Signal • The information transmitted by a telecommunications system can originate in two fundamental forms—digital and analog. • Digital is represented by a string of bits • Analog is represented by the continuous variation of the data.

14. In the most common system, multiple television channels (as many as 500) are distributed to subscriber residences through a coaxial cable, which comes from a trunkline supported on utility poles originating at the cable company's local distribution facility, called the headend. Multiple channels are transmitted through the cable by a technique called frequency division multiplexing.

15. At the headend, each television channel is translated to a different frequency. By giving each channel a different frequency "slot" on the cable the separate television signals do not interfere. As many as 12 channels can be carried in each “slot” also know as a “Digital Rail”. At the subscriber's residence, either the subscriber's television or a set-top box provided by the cable company translates the desired channel back to its original frequency (baseband)

16. Due to widespread cable theft in earlier analog systems, in modern digital cable systems the signals are encrypted, and the set-top box must be activated by an activation code sent by the cable company before it will function, which is only sent after the subscriber signs up. • There are also usually "upstream" channels on the cable, to send data from the customer box to the cable headend, for advanced features such as requesting pay-per-view shows, cable internet access, and cable telephone service.

17. The "downstream" channels occupy a band of frequencies from approximately 50 MHz to 1 GHz, while the "upstream" channels occupy frequencies of 5 to 42 MHz. Subscribers pay with a monthly fee. Subscribers can choose from several levels of service, with "premium" packages including more channels but costing more.

19. Modem • The transmission of digital data (from a personal computer [PC]) can be accomplished on a direct digital basis over a digital circuit or it can be converted to an analog signal with a modulator/demodulator (modem). • These modems convert the digital signal’s 1s and 0s into radio frequencies, and is then transmitted over a standard coax. The process is reversed at the opposite end to recreate the original digital signal.

20. Decibel (dB) • A measure of analog signal strength is a bel, named in the honor of telephone pioneer Alexander Graham Bell. • The term is inappropriately large for ITS work, so a decibel (dB) or one tenth of a bel is used. • It is a ratio signals and may be used for comparing power, current, or voltage. • System gain and attenuation are typically stated as dB gain or dB loss. For example, an amplifier may have a power gain of 10 dB, or a connector in a cabling system may have a loss of 0.3 dB.