10 exam-style questions with answers and explanations, straight from our 1,030-question bank. Tap an answer to check yourself. When you're ready, take the scored version in the free practice test.
The DCI exam has 75 questions and runs 2 hours.
These 10 free DCI questions are organized by exam domain, so you can see how each part of the Data Cabling Installer blueprint is tested. Reveal the answer and explanation under each question.
Rainwater begins collecting in an unshored, 4.5 ft-deep trench while a crew is placing communications conduit. Soil is sloughing from a sidewall, and the competent person is elsewhere on site. The foreman says the trench is too shallow to require action. What should the crew do immediately?
Correct answer: A - Leave the trench and obtain a competent-person reassessment before reentry.
During an access-control retrofit, a two-conductor cable supplies a device from a regulated 24.0 V DC source. The source maintains 24.0 V at its terminals while the device draws 0.40 A. Each conductor has 4.0 ohms end-to-end resistance; connector resistance is negligible. The device requires at least 22.0 V at its input. What does the voltage-drop check show?
Correct answer: A - 20.8 V at the device; the supply path is inadequate.
The power specification for a standards-compliant PoE surveillance camera requires 14 W at the camera's input. Its copper channel may be the full 100 m allowed by the application, and the switch has ample total PoE capacity. Allowing for the IEEE channel-loss allowance, what is the lowest PoE type that can guarantee sufficient power at the device?
Correct answer: B - IEEE 802.3at Type 2
A permanent-link report shows the following results at one test frequency: insertion loss 18 dB, maximum permitted 21 dB; NEXT 38 dB, minimum required 35 dB; return loss 12 dB, minimum required 15 dB. All other required measurements pass. How should the technician interpret the report?
Correct answer: D - FAIL: return loss is too low, so investigate impedance discontinuities.
The inspector finds CMP-rated communications cable in an indoor vertical riser where CMR cable was specified. The project uses the 2020 NEC and permits its authorized cable substitutions; every other material and installation requirement is satisfied. How should the fire-listing difference be treated?
Correct answer: B - Accept it; CMP is permitted as a substitute where CMR is required.
On a 110-style patch panel, several conductors are severed on the incoming-cable side of the insulation-displacement contacts, while the waste tails remain attached. The installer used the correct, undamaged 110 impact blade. Which change in tool use corrects the cause?
Correct answer: D - Face the cutting edge toward the waste tail.
An office installation must support 10GBASE-T over balanced-copper channels as long as 96 m, without intermediate switches or repeaters. What is the lowest TIA-recognized category specified to support this application at that channel length?
Correct answer: C - Category 6A, with transmission performance specified to 500 MHz
A 10 Gb/s fiber uplink will not establish a link. One switch has an 850 nm 10GBASE-SR module; the other has a 1310 nm 10GBASE-LR module. The installed duplex OM3 fiber is approved for SR operation at this distance. Connector cleanliness and transmit-to-receive polarity are verified, and both switch ports support the required SR modules. Choose the least disruptive standards-compatible correction.
Correct answer: C - Replace the LR module with a compatible 850 nm SR module.
A proposed Category 6 horizontal channel contains 92 m of fixed cable, including service loops, a 2 m equipment cord in the telecommunications room, and a 4 m work-area cord. The designer says, 'The total is only 98 m, so it complies.' No special length allowances apply. Which revision actually resolves the problem?
Correct answer: B - Reroute the fixed run to 88 m and retain the 6 m of cords.
A basic DC continuity tester shows all eight conductors connected straight through, with no opens or shorts, but the new link fails NEXT badly. Inspection finds the same arrangement at both ends: pins 3 and 6 carry white/green and solid blue; pins 4 and 5 carry solid green and white/blue. Which termination fault explains these findings?
Correct answer: C - Split pairs involving the green and blue conductors
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