C-7 Low Voltage Systems exam questions, with answers
10 practice questions for the CSLB Low Voltage Systems trade exam, each with the answer, a plain explanation and the source it rests on.
These are not real exam questions. CSLB does not release its test questions or answer keys, and nobody else has them. We write our own questions from the C-7 outline and the codes, standards and references CSLB lists for the exam. Each answer names its source so you can check it.
The C-7 exam has 7 sections. The questions below are grouped by section, with the share of the exam each one carries. Read the question, pick an answer, then open “Show the answer”. The other questions of the free test, scored section by section, are in the free 25-question C-7 test.
Job Planning and Design · 18% of the exam
Interpreting plans and specifications; planning wire routes and equipment locations; compliance with codes and industry standards; impact on other trades; integration of new and existing infrastructure.
1. Your crew will run a new communications cable on a joint utility pole that also carries electric light and power conductors. Under the NEC rules for overhead communications wires and cables, where should the communications cable go?
- Below the power conductors where practicable, and never on a power cross-arm
- On the same cross-arm as the power conductors, with insulators at each support
- At the same height as the power conductors, kept 12 in from the closest one
- Above the power conductors where practicable, so it stays clear of line work
Show the answer
Answer: A. 2023 NEC (NFPA 70) 800.44(A)(1) says that where communications and power conductors share a pole or run in the same span, the communications wires and cables are placed below the electric light or power conductors where practicable, and 800.44(A)(2) forbids attaching them to a cross-arm that carries power conductors. Above the power, on its cross-arm or level with it all put the communications work inside the power space.
2. You are planning horizontal Cat 6 routes through the space above the ceiling of a single-story warehouse that gets very hot in summer. According to the FOA's guide to installing UTP cabling, what is the concern with routing the cables there?
- The heat lowers the cable's attenuation, so the links may safely run past standard length
- The heat affects the jacket but not the pairs, so a listed cable keeps full standard length
- The heat matters during the pull, so links keep full standard length if pulled under 25 lb
- The heat raises the cable's attenuation, so the links may not support full standard length
Show the answer
Answer: D. The FOA's guide to installing UTP cabling says cables should be kept dry and at moderate temperatures, and that the space above the ceiling in some buildings in hot climates gets very hot, which gives UTP cable higher attenuation so it will not support full standard link distances. Plan the route with that in mind. Heat does not lower attenuation, and neither a listing nor a pull under the FOA's 25 lb tension limit removes the effect.
Source: FOA Reference Guide, Installing UTP Cabling (cable routes kept dry and at moderate temperatures)
Material Selection and Estimation · 15% of the exam
Materials and their applications; tools and equipment and their applications; estimating project costs and preparing proposals.
3. A Class 3 circuit inside a building will be wired with single conductors instead of a multiconductor cable. Under 2023 NEC 722.179(A)(8), what must those single conductors be?
- Type CL2, not smaller than 18 AWG
- Type CL2, not smaller than 24 AWG
- Type CL3, not smaller than 22 AWG
- Type CL3, not smaller than 18 AWG
Show the answer
Answer: D. 2023 NEC (NFPA 70) 722.179(A)(8) says Class 3 single conductors used as other wiring within buildings must be Type CL3 and not smaller than 18 AWG. CL2 is a Class 2 cable type and cannot stand in for Class 3 conductors, and 22 or 24 AWG is below the minimum size for these single conductors.
Wire/Cable Installation and Termination · 12% of the exam
Laying out, installing and supporting pathways; tools and methods of termination; placement and termination of wires and cables; labeling schemes.
4. A listed riser cable routing assembly will carry data cables up a shaft wall from floor to floor, and its listing gives no other support interval. Under 2023 NEC 800.110(C)(2), how must this vertical run be supported?
- At intervals not over 6 ft, with no more than two joints between supports
- At intervals not over 10 ft, with a support placed at every joint in the run
- At intervals not over 4 ft, with no more than one joint between supports
- At intervals not over 3 ft, with no more than one joint between supports
Show the answer
Answer: C. 2023 NEC (NFPA 70) 800.110(C)(2) says vertical runs of cable routing assemblies are supported at intervals not exceeding 1.2 m (4 ft), unless listed for other intervals, with no more than one joint between supports. The 3 ft interval (with supports at each end and joint, and never over 10 ft) is the rule for horizontal runs in 800.110(C)(1).
Systems Configuration and Installation · 16% of the exam
Equipment room components; satellite, CCTV, telephone, data, instrumentation, battery, audio/video and fiber optic systems; building automation; IP networking and VoIP configuration.
5. A satellite dish lead-in must pass near open 120/240 V service conductors (less than 250 V between conductors), and the closeness cannot be avoided. Under 2023 NEC 810.13, what minimum clearance must the installation keep from those conductors?
- 2 ft
- 4 ft
- 6 ft
- 10 ft
Show the answer
Answer: A. 2023 NEC (NFPA 70) 810.13 says outdoor antenna and lead-in conductors must not cross over open electric light or power conductors and must be kept well away from them; where nearness to open service conductors of less than 250 V between conductors cannot be avoided, the installation keeps a clearance of at least 600 mm (2 ft). Where practicable, the antenna conductors also should not cross under the power conductors.
6. You are laying out a campus network that gives each building one /24 subnet for its cameras, phones and controls, all taken from the private block 172.16.0.0 to 172.31.255.255 (the 172.16/12 prefix). RFC 1918 describes this block as 16 contiguous class B networks, and each class B (/16) network holds 256 /24 subnets. How many /24 subnets does the whole block provide?
- 16
- 256
- 4,096
- 65,536
Show the answer
Answer: C. RFC 1918, section 3, reserves 172.16.0.0-172.31.255.255 (the 172.16/12 prefix) for private networks and describes it as a set of 16 contiguous class B network numbers. Each /16 holds 256 /24 subnets, so 16 x 256 = 4,096 (the same as 2^(24-12)). 16 counts only the class B networks, 256 counts the subnets in just one of them, and 65,536 is the number of addresses in one /16, not a count of subnets.
Source: IETF RFC 1918, section 3 Private Address Space (172.16/12 block)
Testing and Project Closeout · 17% of the exam
Tools and methods used to test low voltage equipment; project closeout, documentation and training.
7. You have set the 0 dB reference on a fiber light source and power meter and begun loss testing a building's links. Between links, a helper wants to unplug the launch reference cable from the source to clean it. According to the FOA quickstart guide to cable plant testing, how should the launch cable be handled?
- Disconnect it at the source only when you change wavelength during the test
- Leave it connected to the source for the whole test once the reference is set
- Unplug and clean it at the source end before each link to keep readings steady
- Swap it for a new launch cable every few links to spread the wear on the cords
Show the answer
Answer: B. The FOA quickstart guide says to attach the launch cable to the source and that it should remain connected to the source for the duration of the test; the 0 dB reference is set with it in place, and the guide adds checking that reference periodically. Unplugging, swapping or reconnecting it at the source disturbs the setup that the reference depends on.
Source: FOA Quickstart Guide, Testing A Fiber Optic Cable Plant: Test Procedure, step 2
8. Your C-7 firm's job on a private office building stalled: all trades stopped work, the owner never moved in, and no notice of completion or cessation was recorded. Under Civil Code 8180, after how many days of continuous cessation of labor does completion of the work of improvement occur?
- 15 days
- 30 days
- 60 days
- 90 days
Show the answer
Answer: C. Civil Code 8180(a)(3) makes a cessation of labor for a continuous period of 60 days one of the events that counts as completion of a work of improvement. 30 days is the cessation period after which a notice of cessation may be recorded, and only its recording counts under 8180(a)(4); 15 days is the window an owner has to record a notice of completion (8182), and 90 days is a lien deadline, not a completion event.
System Troubleshooting, Repairs, or Replacements · 7% of the exam
Troubleshooting various problems and making repairs or replacements.
9. Your crew moved an IP camera from a switch on the second-floor camera subnet to a switch in another IDF that serves a different subnet. On boot, the camera asks the DHCP server to confirm the address it used before, and the server answers with a DHCPNAK message. Under RFC 2131, what does this mean and what must the camera do?
- The server is busy with other clients; it must wait and then ask again for the same address
- Its old address is not valid on this subnet; it must drop it and start over for a new one
- Its old address is still valid on this subnet; it must keep it until the old lease runs out
- Another device already uses its old address; it must send a DHCPDECLINE to the server
Show the answer
Answer: B. RFC 2131, section 3.2, says a server should answer with DHCPNAK when the client's request is invalid, for example because the client has moved to a new subnet. A client that receives a DHCPNAK cannot reuse its remembered address; it must request a new one by restarting the full configuration process. DHCPDECLINE is what a client sends when it finds its assigned address already in use, and asking again for the same address only repeats the rejected request.
Source: IETF RFC 2131, section 3.2 (reusing a previously allocated address; DHCPNAK)
Safety · 15% of the exam
Cal/OSHA regulations; identification of job site hazards; safe work practices.
10. Your installer climbs an extension ladder from a warehouse floor onto a mezzanine to pull cable. Under 8 CCR 3276, how far must the ladder's side rails extend above the mezzanine landing surface, unless the top is secured and a grab-rail is provided instead?
- 36 in
- 42 in
- 48 in
- 60 in
Show the answer
Answer: A. 8 CCR 3276(e)(11) says that when a portable ladder is used to reach an upper landing, the side rails extend not less than 36 inches above the landing surface; where that is not possible, the ladder is secured at its top to a rigid support and a grasping device such as a grab-rail is provided. The extra extension must not let the ladder slip off its support under load.
Source: 8 CCR 3276(e)(11) Access to Landings, Cal. Code Regs. Title 8 ยง3276, Portable Ladders (Cal/OSHA)
Where to go from here
How the license works, from experience to fees: how to get a C-7 license. Everything about the course: the C-7 exam page.
Questions from our free C-7 test, written from CSLB License Examination Study Guide, Low Voltage Systems (C-7), form 13E-7 (03-2026), for examinations scheduled on or after October 1, 2023. CSLB notes that the percentages are approximate. Reviewed 14 October 2026. Study guidance only; we are not affiliated with CSLB or PSI.