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The GCT1 exam has 75 questions and runs 2 hours.
These 10 free GCT1 questions are organized by exam domain, so you can see how each part of the General Communications Technician - Level 1 (GCT1) blueprint is tested. Reveal the answer and explanation under each question.
The AC breaker feeding a communications rack has been locked open for a power-supply replacement. Before removing a DC output lead, the technician sees that a battery string also feeds the same bus. What must happen before that lead is disturbed?
Correct answer: A - Isolate and secure the battery feed, control stored energy, and verify deenergization.
A mobile radio needs at least 11.5 V at its terminals in transmit mode. Its regulated supply maintains 13.0 V under load. Total current is 8.0 A during transmission or 1.5 A during reception; the positive and return conductors each have 0.08 Ω resistance, including connections. Use voltage drop = current × loop resistance and neglect other losses. What should the installation record show for transmission?
Correct answer: C - 11.72 V; the minimum is met.
An alarm input expects a closed dry-contact loop while the site supply is healthy and reports an alarm if that loop opens. A nonlatching changeover relay is energized by the healthy supply and drops out when the supply fails. Wire the monitoring loop between:
Correct answer: B - Common and normally open.
A battery controller disconnects its load below 23.0 V and reconnects it above 25.4 V. An outage reduced the battery to 22.4 V and the load disconnected. With normal charging restored, the battery is now rising through 24.6 V, but the load remains off. Which service entry fits this state?
Correct answer: B - Normal hysteresis; continue charging toward the configured reconnect threshold.
A proposed P25 Phase 2 upgrade must carry two simultaneous voice conversations within one assigned 12.5 kHz radio channel. The channel assignment will not change. Identify the operating description that supports this design.
Correct answer: A - Two voice paths use different time slots on the same RF channel.
Dispatch speech is clear on a replacement mobile only when receive tone squelch is bypassed. The repeater requires an 82.5 Hz input tone and transmits a 100.0 Hz output tone. The mobile transmits 82.5 Hz but decodes 123.0 Hz. To restore dispatch audio while preserving repeater access and selective reception, what should be reprogrammed?
Correct answer: D - Change only the receive-tone setting to 100.0 Hz.
After a feeder is replaced with a longer run of the same coaxial cable, transmitter-end return loss improves but field coverage weakens. Transmitter output, the antenna and its mounting are unchanged. Which explanation accounts for both observations?
Correct answer: A - More loss attenuates both the outgoing signal and the returning reflection.
Weak field units become unintelligible whenever a nearby transmitter on another frequency keys up. Inserting a matched broadband 10 dB attenuator ahead of the receiver makes the wanted signal weaker on the meter, yet restores clear speech. Which diagnosis best explains that improvement?
Correct answer: D - Receiver overload is impairing reception of the wanted signal.
A radio-over-IP interface at 192.168.40.20/24 communicates with devices on its LAN but cannot reach its controller at 192.168.50.10. The reachable local router, 192.168.40.1, already has a working route to that controller. The interface has only a local-subnet route and no gateway address configured. Which entry supplies the missing path?
Correct answer: D - Enter 192.168.40.1 as the gateway address.
Commissioning measurements on a short 1310 nm single-mode link show −1 dBm at the receiver-end cable. The receiver accepts −20 to −3 dBm, and the link is losing frames. The power meter is calibrated for 1310 nm; fiber type, connector compatibility and end-face cleanliness have been verified. The appropriate optical correction is to:
Correct answer: C - Install a properly sized, compatible attenuator at the receiver.
The GCT1 exam also covers these domains. Drill them in the full free practice test:
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