BDS Customer Premises Equipment and Drop Systems 2

Question 1

A cable modem shows a downstream power level of +12 dBmV. What should the technician do?

Accepted Answer

Add a signal attenuator at the modem input to bring the level into range

Answer

A downstream level of +12 dBmV exceeds the DOCSIS upper limit (typically +15 dBmV) and is above the optimal range; a small attenuator at the modem input will bring it into specification.

Question 2

What is the purpose of a high-pass filter (HPF) installed at a customer's set-top box or cable modem?

Accepted Answer

To block upstream return path signals from unauthorized devices

Answer

High-pass filters (set-top box filters or traps) block the 5–42 MHz upstream return band, preventing unauthorized or defective CPE from injecting noise or interference into the return path.

Question 3

What causes a 'stairstep' pattern in the upstream power levels across multiple modems in a node service area?

Accepted Answer

Ingress or noise in a portion of the plant is causing some modems to increase their transmit power to overcome the impairment

Answer

A stairstep pattern in upstream modem transmit power indicates a localized impairment (noise, ingress, or high loss) in a branch of the plant where modems must compensate by raising their power.

Question 4

What is the maximum recommended number of passive splitters in a standard residential drop installation?

Accepted Answer

2 (providing up to 4 outputs)

Answer

Best practice limits residential drops to two cascade splitter stages (typically yielding up to 4 outlets) to keep signal levels above the minimum threshold without requiring in-home amplification.

Question 5

What is DOCSIS ranging and why is it important?

Accepted Answer

A process where modems adjust their upstream transmit timing and power so all signals arrive at the CMTS at the correct time and level

Answer

Ranging is the DOCSIS initialization process where the CMTS measures round-trip delay and signal level, instructing each modem to adjust its timing offset and transmit power so all upstream bursts arrive synchronized at the CMTS.

BDS - Broadband Distribution Specialist Practice Test

BDS - Broadband Distribution Specialist Practice Test

BDS Customer Premises Equipment and Drop Systems 2