troubleshooting advanced services
After a digital TV (DTV) service problem has been analyzed and possible causes considered, what is accomplished by isolating the various network elements?
It narrows the scope of likely problem sources.
What is the minimum Wi-Fi signal strength for reliable, timely delivery of streamed Internet protocol television (IPTV) content?
-67 to -65 decibels milliwatt (dBm).
When using a digital signal analyzer to troubleshoot data throughput in the Data Over Cable Service Interface Specification (DOCSIS) network, what is the minimum modulation error ratio (MER) into the cable modem for a 256- quadrature amplitude modulation (QAM) carrier?
32 dB or greater.
Using a 77HP-G tone generator in the Off/Polarity position to test a telephone line for voltage and polarity, what does a bright green light emitting diode (LED) indicate?
A clear working line with correct polarity.
What would be the downstream throughput if two quadrature amplitude modulation (QAM) channels with a throughput of 38 megabits per second (Mbps) were bonded?
76 Mbps.
Which of the following is a form of isolating elements during troubleshooting?
Eliminating possible causes.
What other device factors determine what speeds a device will achieve over a Wi-Fi network?
Processor and storage read/write space
Which 802.11 standard takes more time to send and receive data, thus causing congestion on the 2.4 GHz band?
802.11b
Which of the following channels represents a well performing network?
A channel that is utilized less than 50% of the time
When troubleshooting a modular wall jack that is connected to the telephone using an insulation displacement connection (IDC), what should be used to gain electrical access to the wall jack's pins?
A modular plug break-out adaptor (banjo).
If there are problems with a customer's telephone line, which equipment should be used to monitor a telephone line, check line polarity, place and receive calls, and troubleshoot various faults?
A telephone test set.
What component is built into the VDV II Pro and is used when testing for length measurements in coaxial and twisted-pair cable?
Time domain reflectometer (TDR).
What does a flashing Tel or Voice indicator on an embedded multimedia terminal adapter (EMTA) indicate?
AC power failed and the EMTA is running off the battery.
What is the likely problem when there is dial tone on one phone connected to an outlet, but not on two other phones connected to two different outlets?
An open circuit caused by a break in a conductor, poor contact in a modular connector, or an incorrect wire connection.
What non-Wi-Fi device utilizes 20 MHz of spectrum, which is nearly the same as a Wi-Fi network and, due to its heavy utilization, can cause a Wi-Fi network to stop working entirely?
Analog wireless security camera
What type of applications are error vector magnitude (EVM) expressions best suited?
Applications that have small random noise-like errors.
When performing a wire identification test, using a 77HP-G tone generator and the 200EP-G inductive amplifier probe to locate a tone signal at any point along a cable, distribution device, or at a modular telephone jack, how do you identify the wire?
By touching the tip of the inductive amplifier probe to the signal-carrying conductor.
Why do digital modulation channels have measurable analog parameters?
It is based on modulating an analog RF carrier with digital data.
What type of digital television (DTV) artifact describes moving lines and changing colors across patterns with repeated symmetrical detail?
The moiré effect.
What is the maximum signaling rate for a 3SS device (premium laptop)?
195 megabits per second (Mbps)
What could you do if there are no good channel options in the 2.4 GHz band for your customer's 802.11n device?
If available, connect devices with Ethernet
What should be checked as a possible cause of hum on a customer's telephone line?
Shielding problems in the station wiring, poor terminations, or poor grounding and bonding connections.
Which of the following digital TV (DTV) trouble calls could have been avoided with customer education about the product?
The digital set-top box (STB) overheats.
If the telephone wiring is in the bus topology and the twisted-pair cable tester is connected at the embedded multimedia terminal adapter (EMTA) with the remote unit connected to the last outlet in the loop, what is the quickest way to locate the incorrectly wired outlet if the tester indicates a wiring error?
Break the loop into smaller sections and retest the two sections to identify which one has the wiring error. Continue to divide the section with the error into smaller sections until the wiring error is identified.
If a High-Definition Multimedia Interface (HDMI) splitter is suspected as the cause of a problem, how can the splitter be tested?
Bypass the splitter by connecting only one device at a time using the same HDMI cable.
What should be checked if the DS indicator LED on an embedded multimedia terminal adapter (EMTA) flashes continuously?
Check and diagnose the incoming signal using a signal level meter (SLM).
What does a hole in the center of the quadrature amplitude modulation (QAM) constellation symbol error cloud indicate?
Coherent interference from ingress, or a beat from another channel modulator, landing inside the QAM channel.
In a Data Over Cable Service Interface Specification (DOCSIS) network, why is the data throughput over the return or upstream path typically less than the throughput of data over the forward or downstream path?
Compared to the downstream path, the narrower bandwidths and lower orders of modulation used to transport data over the return path cause the downstream and upstream data throughput to be unequal or asymmetrical.
When replacing a splitter to resolve a digital TV (DTV) service problem, what does confirming the splitter output levels before attaching the output connectors do?
Confirmation reinforces the technician's confidence that the problem will be resolved by replacing the splitter.
What must a technician be aware of when analyzing a digital TV (DTV) problem?
There is frequently more than one contributor to a specific DTV service problem.
What is a possible solution for a customer having intermittent one-way telephone calls?
Tighten all RF connectors and terminate unused outlets, as this will prevent noise or ingress from intermittently entering the return path.
When do the telephone ports on the embedded multimedia terminal adapter (EMTA) receive their Internet protocol (IP) addresses and configuration files?
When the Online indicator is flashing, which is after the modem side of the EMTA receives its IP addresses and configuration files from servers in the headend.
With the Fluke TS19 telephone test set, what does placing the Hi Z/Ring/Talk switch in the "Talk" position establish?
Establishes an off-hook condition for dialing and talking.
What should the technician do if the main telephone port on the embedded multimedia terminal adapter (EMTA) has a failure due to faulty provisioning?
Contact the call center and make sure that the EMTA's media access control (MAC) address matches the address in the operator's database.
During which step of the six-step troubleshooting process for a digital TV (DTV) service problem are quadrature amplitude modulation (QAM) channel measurements typically taken?
Diagnosing symptoms.
In unshielded twisted-pair (UTP) cable, what is the term that describes when an information-carrying conductor makes contact with a grounded conductor?
Ground fault.
What does the two-way capabilities of the High-Definition Multimedia Interface (HDMI) enable to protect full-resolution high definition television (HDTV) content from being copied and sold illegally?
High-bandwidth digital content protection (HDCP).
What does the modulation error ratio (MER) measurement of a quadrature amplitude modulation (QAM) channel tell a technician?
How close the QAM channel is to the cliff where the number of bit errors exceeds the forward error correction (FEC) capacity of the receiver and reception stops.
In an adaptive equalizer display, what do the vertical bars to the right of the incident signal, the eighth bar from the right, represent?
How much equalization is being applied to the channel.
How does Internet protocol (IP) multicast differ from IP broadcast?
IP multicast traffic is only sent to specific modem addresses on the network; IP broadcast traffic is sent to all modems on the network.
When checking the in-channel frequency response (ICFR) of a quadrature amplitude modulation (QAM) channel in the customer premises, a frequency response with a repetitive ripple is a symptom of what?
Micro-reflections.
When diagnosing an Internet protocol television (IPTV) service problem in the customer premises, what can be concluded if the problem goes away when the streaming media player is connected to the local area network (LAN) with an Ethernet cable rather than Wi-Fi?
The problem is isolated to the Wi-Fi network.
Why does the information in set-top box (STB) and modem diagnostic screens often appear cryptic to a customer?
The screens use initials, acronyms, and jargon intended for people that are familiar with the product.
When using an inductive amplifier probe to identify a pair of wires, what is the purpose of shorting the leads of a tone-carrying pair?
The short cancels the induced tone on the pair of wires, thus the correct pair is identified when the tone disappears.
Why is switching the Wi-Fi frequency of a streaming media player to the 5 gigahertz (GHz) band a possible solution to avoid interference from neighboring networks?
The signal propagation at 5 GHz is lower and interference from neighboring networks is less likely than at 2.4 GHz.
When analyzing a problem, what can the technician learn by asking the customer to show or demonstrate the problem?
The symptoms of the problem can be viewed, and any unusual screens or customer entries can be identified.
In the customer premises, what could cause some dual tone multifrequency (DTMF) touch-tone telephones to have continuous dial tone caused by polarity reversal, but not other DTMF telephones?
The telephone wiring polarity is incorrect, and the customer has a mix of older and newer DTMF touch-tone telephones.
What enables assessment of upstream Data Over Cable Service Interface Specification (DOCSIS) channel parameters using the quadrature amplitude modulation (QAM) analyzer function of a signal level meter (SLM)?
The upstream channels from the built-in DOCSIS modem are optimized for the upstream path and the channel parameters displayed by the instrument.
What is the likely problem if the DS indicator on an embedded multimedia terminal adapter (EMTA) continuously blinks slowly and never progresses to another stage?
There is either no Data Over Cable Service Interface Specification (DOCSIS) carrier or the DOCSIS carrier is not being recognized by the EMTA.
Which characterizes a quadrature amplitude modulation (QAM) channel?
When of equal amplitude and bandwidth, the power level of a QAM channel is several decibel (dB) higher than an analog TV channel.
In the PacketCable architecture, what is the purpose of the embedded multimedia terminal adapter (EMTA)?
To provide an interface between the customer's telephone and the hybrid fiber/coax (HFC) network of the broadband cable operator.
What layers of the Open Systems Interconnection (OSI) reference model are specific to cable networks and are present only between Data Over Cable Service Interface Specification (DOCSIS) modems and the cable modem termination system (CMTS)?
Layers 1 through 4 (Physical layer, Data Link Layer, Network Layer, and Transport Layer) are applied between the DOCSIS modem and CMTS.
When interpreting test results on the VDV II Pro, what does it mean if both rows of pins on the light emitting diode (LED) display are identical?
It indicates straight-through wiring and that the cable tested is correctly "pinned" and electrically continuous without open or short circuit conditions.
When performing a voice cable test using a VDV II Pro and voltage detection shows that you have greater than 30 volts (V) on Pins 3 and 4, what detected service does this indicate?
Private Branch Exchange (PBX).
How is silver satin cable used to connect telephone equipment to wall outlets typically pinned?
Reversed at opposite ends, or cross-pinned.
When troubleshooting a digital TV (DTV) authorization issue, what can be verified using the set-top box (STB) diagnostic page?
STB reception of authorization message data.
Which of the following characterizes the successful troubleshooter?
Someone with an inquisitive and relentless desire to solve and fix problems.
What could be done if Co-channel interference is found to be the reason for slower data rates?
Switch the network to another channel that is less congested
A narrow slice of spectrum appears on the 2.4 GHz band that may or may not cause congestion when this button is pressed on a 2.4 GHz cordless phone?
Talk
What does a good modulation error ratio (MER) measurement of a quadrature amplitude modulation (QAM) channel with digital television (DTV) artifacts indicate?
The artifacts are created before modulation.
When locating a short circuit using a telephone test set, open one side of the telephone line at any location and place the telephone test set in the loop—one lead connected to each side of the opened line. A loud click can be heard on which side of a fault if the circuit is closed?
The battery side of a fault.
What is the first step a modem does when attempting to register with the cable modem termination system (CMTS)?
The modem sends a dynamic host configuration protocol (DHCP) request for an Internet protocol (IP) address to the CMTS, which forwards the request to the DHCP server.
What was introduced in Data Over Cable Service Interface Specification (DOCSIS) 3.0 to allow enough bandwidth for upstream carriers from previous DOCSIS versions?
The option to increase the top frequency of the upstream to 85 MHz.
When a test instrument indicates measurements that fall outside of minimum or maximum requirements, why should a technician recognize what the failed measurements are?
To troubleshoot and resolve the cause of failed measurements.
What should you do if a client device keeps defaulting to the 2.4 GHz network over the 5 GHz network?
Use different service set identifiers (SSID) for each network
How should the digital multimeter (DMM) be used to troubleshoot problems in the telephone wiring?
Use the voltmeter function; both the network interface device (NID) and the embedded multimedia terminal adapter (EMTA) provide a steady on-hook voltage.
After resolving the problem with the premises wiring issue, which of the following is the next step in the six-step process that the technician should take?
Verify that the problem has been resolved and that phone service is running perfectly on all phones.
Although the cables seldom cause a High-Definition Multimedia Interface (HDMI) interoperability issue, why is it still a good practice to swap cables?
It is usually easy and eliminates the HDMI cable as a potential cause of an interoperability problem.
What are two features that were added in Data Over Cable Service Interface Specification (DOCSIS) 3.1 to extend the viability of hybrid fiber/coax (HFC) networks into the next decade?
Orthogonal frequency division multiplexing (OFDM) and low-density parity-check (LDPC).
What does it mean when the embedded multimedia termination adapter's (EMTA) Online light emitting diodes (LED) is blinking fast during registration?
The Data Over Cable Service Interface Specification (DOCSIS) cable modem is acquiring an upstream lock.
What is the difference between the wiring configurations for a residential, 8-position, 8-contact (8P8C) modular plug and jack in the Universal Service Order Codes (USOC) and ANSI/TIA/EIA 570-B?
The placement of pair numbers 3 and 4.
When analyzing loss of lip sync at the customer premises, what does seeing the same issue on multiple channels tell you?
The problem is coming from the set-top box (STB), TV, or other equipment in the customer premises.
A customer reports a problem of no dial tone (NDT). Upon inspection, the technician notices that new carpeting has been installed. What should the technician do next?
Look for a cable that runs under the carpet; it is likely that the cable has a short from the carpeting tack strip.
When troubleshooting a telephone service problem in the customer premises, what is the best way to identify the problem?
Talk to the customer, ask what they are experiencing, and listen carefully to their answer.
Which Data over Cable Service Interface Specification (DOCSIS) layer is used by the cable modem termination system (CMTS) to differentiate between cable modems?
The DOCSIS Media Access Control (MAC) Layer.
Because the spectral density of a quadrature amplitude modulation (QAM) channel is much higher than that of an analog TV channel, what is done to ensure equal power in all channels in a network with analog and digital modulation channels?
Operate the analog TV channels at higher amplitude level than the QAM channels.
Which type of set-top box (STB) operates more like Data Over Cable Service Interface Specification (DOCSIS) cable modems with return channels on the same frequencies used for cable modems?
STB with DOCSIS Set-top Gateway (DSG) client software and embedded DOCSIS modems.
What should a technician do if Wi-Fi signal strength appears to be too low for what the customer is trying to use the network for?
Set expectations with the customer by explaining the signal strength issue
What does a set-top box (STB) diagnostic page of a quadrature amplitude modulation (QAM) channel showing signal-to-noise ratio (SNR) near or below 30 dB indicate?
The QAM channel quality is on the edge for reliable reception, and the source of the problem is likely in the distribution network or customer premises.
Which step in the troubleshooting process requires a discussion with the customer to gather more detail about the problem?
Step 1: Identify the problem.
