BDS Customer Premises Equipment and Installation 2 — Questions and Answers
Question 1: What does the upstream transmit power level of a cable modem indicate about the drop?
- Higher transmit power means the modem is downloading faster
- High transmit power (near or above 51 dBmV) indicates the modem is compensating for excessive signal loss in the drop or plant (Correct answer)
- Low transmit power means the modem is malfunctioning
- Transmit power level is unrelated to drop condition
Correct answer: High transmit power (near or above 51 dBmV) indicates the modem is compensating for excessive signal loss in the drop or plant
A cable modem increases its transmit power during ranging to overcome high losses in the subscriber drop or distribution plant; levels consistently near the maximum (51–54 dBmV) indicate excessive attenuation that should be investigated.
Question 2: What is a cable set-top box (STB) and what are its main functions?
- A device that converts coaxial signals to wireless Wi-Fi for the TV
- A customer premises device that tunes, decrypts, and decodes cable video channels for display on the television (Correct answer)
- A headend device that encodes video for distribution
- A modem that combines internet access with cable TV reception
Correct answer: A customer premises device that tunes, decrypts, and decodes cable video channels for display on the television
A set-top box tunes to a specific downstream channel, decrypts the conditional access-protected content, decodes the MPEG video stream, and outputs audio/video to the connected television.
Question 3: What is a CableCARD and why was it introduced?
- A physical access card that subscribers use to pay their cable bill
- A removable conditional access module that allows retail TVs and devices to receive encrypted cable channels without a set-top box, mandated by the FCC to promote retail equipment (Correct answer)
- A network management card installed in the CMTS for cable modem provisioning
- A memory card for storing DVR recordings
Correct answer: A removable conditional access module that allows retail TVs and devices to receive encrypted cable channels without a set-top box, mandated by the FCC to promote retail equipment
CableCARD is a PCMCIA-style card that contains the conditional access credentials, allowing consumers to use retail TVs and TiVo-style DVRs with cable service without renting an operator's set-top box.
Question 4: What is a whole-home DVR gateway and how does it differ from a single-room DVR?
- A whole-home gateway is located at the headend; a single-room DVR is at the customer premises
- A whole-home DVR gateway centrally records content and streams it to client devices throughout the home; a single-room DVR can only play recordings on the TV it is connected to (Correct answer)
- A whole-home gateway uses fiber to the home; single-room DVRs use coax
- Whole-home gateways provide internet; single-room DVRs only provide TV
Correct answer: A whole-home DVR gateway centrally records content and streams it to client devices throughout the home; a single-room DVR can only play recordings on the TV it is connected to
A whole-home DVR gateway centralizes recording and streaming, allowing multiple thin-client set-top boxes in any room to access recordings or live TV channels served from the gateway over the home's coax or Ethernet network.
Question 5: What causes a cable modem to repeatedly log T3 timeout errors?
- The modem's firmware needs updating
- The modem is not receiving a response to its upstream ranging requests, typically caused by upstream plant impairments, high noise, or incorrect upstream channel assignment (Correct answer)
- The subscriber has exceeded their data cap
- The downstream channel has too many QAM channels bonded
Correct answer: The modem is not receiving a response to its upstream ranging requests, typically caused by upstream plant impairments, high noise, or incorrect upstream channel assignment
T3 timeouts occur when a cable modem sends a ranging request (RNG-REQ) but does not receive a ranging response (RNG-RSP) from the CMTS, usually due to upstream path impairments preventing the burst from reaching the headend.
Question 6: What is the role of a splitter versus an amplified distribution amplifier for in-home wiring?
- Splitters are for upstream; amplifiers are for downstream only
- A passive splitter simply divides signal power (adding loss), while an amplified distribution amplifier compensates for that split loss with gain, maintaining adequate signal levels at multiple outlets (Correct answer)
- Splitters support HD channels; amplifiers are for SD only
- Amplifiers encrypt the signal; splitters do not
Correct answer: A passive splitter simply divides signal power (adding loss), while an amplified distribution amplifier compensates for that split loss with gain, maintaining adequate signal levels at multiple outlets
When a drop feeds multiple TV outlets, each passive split adds 3–4 dB of loss; an active distribution amplifier provides enough gain to overcome the split losses and deliver proper levels at each outlet port.
BDS Customer Premises Equipment and Installation 2
What does the upstream transmit power level of a cable modem indicate about the drop?