digital technician
Virtually all cable systems carry a combination of analog and digital channels, so standard practice is to operate the digital channels at lower average power levels than the analog channels. For 64-quadrature amplitude modulation (QAM) channels, what do most systems set their average power levels to?
A) 10-decibels (dB) lower than analog.
The Cable Service Interface Specification (DOCSIS) infrastructure is primarily comprised of
A) A cable modem-like device in the customer premises and a cable modem termination system (CMTS) in the headend.
Which of the following best describes unicast distribution?
A) A one-to-one transfer of video-on-demand (VOD) data occurs between the VOD server and client device.
CableCARDs have two primary functions. One is user authentication. What is the other function?
A) Authorizing encrypted video services.
When modifying the application of a digital receiver to that of a test instrument, the quadrature amplitude modulation (QAM) analyzer is very practical. Most QAM analyzers include a spectrum analyzer to enable analog measurement of what?
A) Carrier level, bandwidth, and system noise.
nternet Protocol television (IPTV) utilizes quality of service (QoS) to do which of the following over its private, managed network?
A) Control quality of delivered content.
Logarithms and antilogarithms allow signals to be more easily added and subtracted together or have their amplitude and power multiplied and divided. What does an antilogarithm convert?
A) Decibel (dB) values to power and voltage units.
Errors can be avoided when measuring signals of different bandwidth by converting all measurements to a common value-per-frequency unit. What measurement removes any errors attributable to bandwidth and allows for comparisons between signals of differing bandwidths?
A) Decibels per millivolt per hertz (dBmV/Hz).
Power can be measured at a particular frequency, spread over a bandwidth, or equal the total power in a network. What measurement unit is used when expressing the power of a signal?
A) Decibels per milliwatt (dBm).
The American National Standards Institute (ANSI) and Society of Cable Telecommunications Engineers (SCTE) developed a number of standards that address digital television (DTV). What do the ANSI/SCTE 130-2008; 30-2007; 67-2006; and 118-2006 standards address?
A) Digital program insertion.
New cable services are implemented based on cost and need. What is a subset of tru2way which will allow cable operators to give customers some of tru2way's function without all of its cost?
A) Enhanced TV Binary Exchange Format (EBIF).
In quadrature amplitude modulation (QAM) bipolar coordinate graphs, all adjacent symbols are different by only one bit. What is this planned condition known as?
A) Gray coding.
Besides challenges to stability, scalability, and issues with end-to-end service reliability and availability, what other technical challenges hindered the initial deployment of Internet Protocol television (IPTV) over a managed network?
A) High infrastructure costs.
Which of the following is a feature of DOCSIS 2.0?
A) IPV4 addressing.
The Motion Picture Experts Group (MPEG) develops standards for digital, compressed moving pictures, and associated audio. Which of the following MPEG standards targets digital television (DTV) applications over the Internet or in mobile devices?
A) MPEG-4.
Visual artifacts are a result of a quadrature amplitude modulated (QAM) downstream signal encountering noise and other radio frequency (RF) impairments. Which of the following is an artifact of overcompression?
A) Macroblocking.
What is one strategy the broadband cable industry is using to retain customers and regain cord-cutters?
A) Provide TV Everywhere (TVE) service.
Statistical multiplexing is not an error-free system. To account for the times when the bandwidth requirements of the statistically multiplexed programs exceed the bandwidth capacity of the system, what process is used?
A) Rate-shaping.
What does Transmission Control Protocol (TCP) add to the headers of each segment that are used by the receiving host to reassemble the segments in the correct order?
A) Sequence numbers.
The forward error correction (FEC) process contains four processing layers. Which layer is a complex error correction scheme that divides the transport stream data packet into blocks of symbols?
A) The Reed-Solomon layer.
What measurement is a true indication of a system's quality and can be used to determine how close a system is to failure?
A) The bit error rate (BER) measurement before forward error correction (FEC).
Power peaks occur randomly, adding to and subtracting from the average power of a quadrature amplitude modulation (QAM) channel. How does the peak power of a QAM channel compare to the channel's average power?
A) The peak power is 6- to 13-decibels (dB) greater than the channel's average power.
A transport stream contains an information table that is necessary for a decoder to sort data and reconstruct a program. In a transport stream header, which field is used by the decoder to indicate the beginning of a transport stream packet?
A) The sync byte field.
The North American quadrature amplitude modulation (QAM) standard specifies two additional layers of processing before and after modulation, MPEG-2 framing and forward error correction (FEC). Which is a function of the MPEG-2 framing layer?
A) To provide additional error correction by utilizing the sync byte.
There are two types of time stamps, the decode time stamp (DTS) and the presentation time stamp (PTS). What is a time stamp used for?
A) To synchronize a decoder to real time.
There are four major forward error correction (FEC) layers: Reed-Solomon, interleaving, randomizing, and trellis coding. Which layer deals with the symbol-to-symbol transitions?
A) Trellis coding.
In a transistor-transistor logic (TTL), each terminal is constantly, and instantaneously, in one of two voltage conditions. What is typically a low voltage state?
B) 0-0.8 volts.
What kind of primary protection is recommended to protect the coax within 50 feet of its entrance to a building?
B) A bonding block.
Which of the following best describes the Open Systems Interconnection (OSI) reference model?
B) A model that organizes the processes of network communications functions and services by network hardware and software into one of seven categories called layers.
In a quadrature amplitude modulation (QAM) signal, the faster the signal transition from one symbol to another, the higher the number of harmonics. In a QAM modulator, what is used to eliminate these harmonics and limit the occupied bandwidth of the channel?
B) A root raised cosine filter.
The return spectrum is in ever-increasing demand as customers' desire to upload more data onto the cable system increases. What is the return path for most North American cable systems defined as?
B) Between 5-42 megahertz (MHz).
Which of the following is an example of how the Connection-Oriented Protocol works?
B) Calling someone on the telephone and saying "hello" before speaking.
Which of the following occurs in the IP Suite model?
B) In a four-layer IP suite, The Network Access Layer is broken into two functional layers creating the five-layer IP suite.
The spectrum analyzer is the instrument of choice for measuring carrier level, noise, and ingress on the return path. What is the max hold or peak hold function on a spectrum analyzer used for?
B) It allows for viewing fast transient signals or noise, which is common on the return path.
ASCII is a seven-bit binary data code. In practice, however, it is coded with eight bits. What is the 8th bit used for?
B) Parity.
The Electronic Industries Alliance (EIA) helps develop standards on electronic components, consumer electronics, electronic information, telecommunications, and Internet security. Which of the following is an EIA standard?
B) RS-232.
Which of the following best describes computer protocols?
B) Rules or standards implemented with hardware, software, or a combination of the two that enable computers to connect and then transfer data to each other.
There are many methods of data compression, each designed to remove redundant data prior to its transmission. Which type of data compression is used by a fax machine?
B) Run-length coding.
The DOCSIS cable modem has two interfaces that connect to two different networks with different protocol stacks: the RF interface to the HFC Network and
B) The Ethernet interface to the customer premises equipment (CPE).
When sending data from one host to another host, during which layer is the IP header information added to become an IP packet that contains both hosts IP addresses?
B) The Internet Layer.
The digital receiver is designed to compensate and correct for reasonable levels of linear distortion and noise that are created in the cable network. Which stage measures and corrects linear distortions before the data goes to the forward error correction (FEC) stage?
B) The adaptive equalizer (AE) stage.
High definition television uses several processes to take the data sent by the cable company and display it on the television set. What happens to the data when it is demultiplexed?
B) The audio and video packets are separated.
Using powers of 10 is a way to work with very small and very large numbers. In the base 10 number 106, what does the exponent value indicate?
B) The decimal point is six places to the right of the one.
The way in which the term bandwidth is used determines its meaning. In the context of digital communications, what is bandwidth used to describe?
B) The information-carrying capacity of a modulation or transport medium.
The pulse code modulation (PCM) process as it relates to digital television (DTV) consists of sampling, quantizing, and encoding. Which process allows for discerning subtle differences, thereby creating the impression of natural voice and imaging?
B) The quantizing process.
The MPEG-2 bit stream provides a means to transport compressed digital television (DTV) data and reconstruct it for totally different applications. For what application is the MPEG-2 Program Stream designed?
B) The storage and retrieval of DTV content.
Which of the following technologies allows Internet access for mobile phone users?
B) Third generation (3G).
Cable Television Laboratories, Inc. (CableLabs) is a nonprofit organization founded by cable operators and funded by fees paid by members (made up entirely of cable companies). What is the primary role of CableLabs?
B) To create specifications and conduct the certification and qualification testing of new telecommunications products.
Which protocol is used for applications that place a higher priority on the delivery of intact and error-free data, such as email and file transfers, and less on timely data delivery?
B) Transmission Control Protocol (TCP).
Quadrature amplitude modulation (QAM) RF carriers utilize multiple levels of amplitude and phase combinations or symbols transmitted in each clock cycle. How wide is each carrier?
C) 6 MHz.
Statistical multiplexing provides the most video services possible within a fixed bandwidth. Which of the following best describes a statistical multiplexer?
C) A dynamic device with the capability of constantly mixing variable bit rate (VBR) programming.
Video-on-demand (VOD) networks operate on an Internet protocol (IP), also known as IP technology. What is IP technology based on?
C) An eight-bit binary number system.
Migrating cable operations to an all-digital platform replaces analog channels with digital channels. For every 6-megahertz (MHz) analog channel that can be replaced with a 256-QAM (quadrature amplitude modulation) digital carrier, how many additional standard channels can be added to the line-up?
C) Approximately seven to twelve.
MPEG compression uses a series of data frames to allow moving pictures to be coded with a minimal amount of data. Which type of data frame contains the least amount of data?
C) Bidirectional coded frame (B-frame).
Amplitude measurements are obtained differently on analog and digital quadrature amplitude modulation (QAM) carriers. How are amplitude measurements on QAM digital carriers obtained?
C) By measuring the average power from the carrier's center frequency to both carrier edges.
In order to more easily discuss and design logic gates, high and low voltage states are designated by a few simple terms. Which of the following can be used to refer to a low voltage state?
C) False.
Noise is a generic term to describe unwanted energy in a system. What type of noise occurs from ingress and is characterized by large unpredictable noise bursts?
C) Impulse noise.
Each of the MPEG standards describes a specific part of the digital coding process. Which standard describes the data transport process?
C) MPEG-2.
Which set of standards allows television sets, set-top boxes (STB), and DVRs in the home to share digital video content with one another?
C) Multimedia over Coax Alliance (MoCA).
By definition, modulation is the process of altering the amplitude, frequency, phase or some combination of these characteristics of the continuous wave (CW) carrier by the coding of a baseband signal. In what type of modulation is the frequency and amplitude the same for a one or zero?
C) Phase shift keying (PSK).
The International Telecommunication Union (ITU) standardization sector develops recommendations that define how telecommunications networks operate and interwork. What does the ITU-R BT.601 recommendation address?
C) Processes for encoding and digitizing an analog video signal, and then editing, processing, and transmitting it.
Which protocol is better suited for the transport of IP video, adding a timestamp and sequence number to real-time applications such as IP video data to enhance their control and synchronization?
C) Real-Time Transport Protocol (RTP).
Theoretically, the required bandwidth for a quadrature amplitude modulation (QAM) channel is equal to the symbol rate. However, when a continuous wave (CW) carrier is amplitude modulated, what results from the modulation process?
C) Sidebands and harmonics.
What organization accredits the procedures of standards developing organizations (SDO), such as the Society of Cable Telecommunications Engineers (SCTE) and the Telecommunications Industry Association (TIA)?
C) The American National Standards Institute (ANSI).
Which of the following organizations manages the international radio frequency spectrum and satellite orbit resources in an effort to avoid harmful interference between radio signals in different countries?
C) The International Telecommunication Union (ITU).
The radio spectrum is the radio frequency (RF) portion of the electromagnetic spectrum. Which agency administers the federal use of spectrum to organizations such as the military, Federal Aviation Administration (FAA), and the FBI?
C) The National Telecommunications and Information Administration (NTIA).
MPEG (Motion Picture Experts Group) digital video compression is called lossy because the data output at the decoder is not identical to the data originally input at the encoder. Which of the following explains why the lost data is not a problem?
C) The human eye cannot detect that the data is missing.
Plain old telephone service (POTS) is the traditional telephone service that, until recently, was the only telephone service. Which of the following is the connection between the customer and the telephone company?
C) The local loop.
Tru2way is a software platform that allows two-way communications between the cable operator and the home. What hardware does it eliminate the need for?
C) The set-top box (STB).
The I carrier is known as the in-phase carrier and the Q carrier is called the quadrature carrier. What is the relationship between these two carriers?
C) They are at the same frequency, 90 degrees out of phase with each other.
Phase noise is an indication of carrier frequency stability. What does phase noise cause the constellation symbol error clouds to do?
C) To create a circular pattern.
Tru2way is a trademark of CableLabs and is the successor of a project known as OpenCable Application Platform (OCAP). What is the goal of Tru2way?
C) To standardize specifications for a new generation of host devices that are interoperable across cable systems.
The time between an incident signal and the tap can be used to identify the approximate location of a micro-reflection. The distance to each micro-reflection can be calculated by multiplying the tap time by the cable's what?
C) Velocity of propagation (VOP).
What are the most common modulation schemes used in broadband cable networks?
D) 64-QAM and 256-QAM.
Radio frequency (RF) amplifier manufacturers build amplifiers with diplex filters designed to various forward and return frequency splits. Which of the following is a common frequency split sometimes used in other parts of the world?
D) A 55/70 split.
As the level of modulation increases, so does the number of bits that are represented by a signal transition. What are transitions representing more than one bit known as?
D) A symbol.
Grooming is one method used to control the content sources on a hybrid/fiber coax (HFC) network. What is grooming also referred to as?
D) Add-drop multiplexing.
A multiplexer ensures that all transport stream packets are 188 bytes. What does the multiplexer do when the header and the payload do not equal 188 bytes?
D) Adds null packets to the adaptation field.
Businesses often have a room that contains the cables and equipment for telephone communications. Which standards are used for the telephone room requirements?
D) American National Standards Institute (ANSI)/Telecommunications Industry Association (TIA)/ Electronic Industries Alliance (EIA).
There are several methods that can be used to make existing bandwidth more efficient. How does the DOCSIS 3.0 specification increase the efficiency of existing bandwidth?
D) By allowing for increased data rates through the use of forward and return channel bonding.
Why is multicast distribution of television content more efficient than broadcast and unicast?
D) Content data is sent only to authenticated clients that request content from the server.
Error correction data enables the receiver to restore bits of data lost during transmission, and reconstruct the original content. At what stage is the error correction data inserted?
D) During the modulation stage.
The modulation process for eight vestigial sideband (VSB) signals has a number of similarities with quadrature amplitude modulation (QAM). However, the 8-VSB modulation process distinguishes itself from the QAM modulation process by adding an Advanced Television System Committee (ATSC) pilot with sync information that does what?
D) Ensures the receiver can identify, lock, and synchronize its internal clock on the channel.
Most electronics used in a cable plant and cable system are designed with integrated circuits (IC). Which statement about the relationship between integrated circuits (IC) and microprocessors is true?
D) Every microprocessor is an IC.
Both carriers in quadrature phase shift keying (QPSK) are amplitude modulated with half of the data stream, then combined together to produce the QPSK symbol. How many amplitude and phase states does a QPSK signal use?
D) Four.
Linear distortion of a received signal is defined as any characteristic change (frequency response, phase, tilt, bandwidth, etc.), other than amplitude, from the transmitted signal. On a digital carrier, what does linear distortion cause?
D) Inter-symbol interference (ISI).
MPEG-4 advanced video coding (AVC) enables HDTV to be compressed more efficiently without a loss of quality. How must MPEG-4 AVC content be transported?
D) On a MPEG-2 transport stream.
Which CableLabs specification is an interoperable interface specification for delivering advanced, multimedia services over two-way cable plant?
D) PacketCable.
The total power in a system is an indication of all of the signals lumped together without regard to individual channel levels. What equation is used to calculate the total power of signals of equal amplitude?
D) Pt = L+10Log10(N)
Which protocol provides quality of service (QoS) monitoring and information that synchronizes multiple real-time transport protocol (RTP) streams?
D) Real-time control protocol (RTCP).
Using algorithms to remove redundancy between video frames makes it possible to transport digital video on multiple mediums without a perceived loss of quality. What inter-coding process between video images uses motion compensation in the time axis to identify redundant information between video frames?
D) Temporal compression.
What American National Standards Institute/Society of Cable Telecommunications Engineers (ANSI/SCTE) standard negates the need for a cable customer to rent a digital set-top box from the cable company?
D) The ANSI/SCTE 40 (2004) Digital Cable Network Interface Standard.
Which of the following organizations has a portfolio of some 900 active standards and has published nearly one-third of the world's technical literature in electrical engineering, computer science, and electronics?
D) The Institute of Electrical and Electronics Engineers (IEEE).
There are seven basic logic gates, each designed to follow a specific rule of Boolean logic. Which logic gate acts as an inverter by reversing the logical input state?
D) The NOT gate
To decode encrypted programming, a decoder must know where to access the entitlement management messages (EMM). Which of the following tables contains the EMM information?
D) The conditional access table (CAT).
What characteristic of a quadrature amplitude modulation (QAM) carrier causes amplitude measurement inaccuracies on conventional spectrum analyzers and signal level meters (SLM)?
D) The energy in a QAM carrier is distributed across the entire bandwidth of the carrier.
The same integrated power measurement techniques used for quadrature amplitude modulation (QAM) and other digital signals are used for 8 vestigial sideband (VSB) signals. What 8-VSB measurement technique shows signal transitions as a signal vector moves from symbol to symbol?
D) The eye diagram.
When delivering phone and data services from the broadband cable headend to the customer premises, the cable modem termination system (CMTS) interfaces to which of the following in the headend?
D) The public switched telephone network (PSTN) and the Internet.
Boolean logic is a form of algebra in which all values are reduced to either true or false. In a NAND gate, which of the following inputs would produce an outcome of false?
D) Two true inputs.
What led to the categorization of TV viewing into two categories, linear and nonlinear?
D) Video-on-demand (VOD).