CSLB C-7 Low Voltage Systems (Trade Exam) — All Questions

Why does the federal criterion specify mesh doors on equipment cabinets?

• a.To let technicians read labels without opening them
• b.To meet the cabinet's bonding requirement
• c.To reduce the cabinet's weight on the floor
• d.For front-to-rear airflow through the equipment✓

The criterion designs cabinets with 63 percent mesh doors, blanks and baffles to ensure front-to-rear airflow and avoid recirculation. Reading labels, bonding and weight are not the stated reasons; bonding is done with conductors and busbars, not door perforation.UFC 3-580-01 (2024), para. 2-3.1.5.4 (equipment cabinets)

Where more advanced cooling schemes are not used, how does the federal criterion arrange equipment rows?

• a.Rows facing the same direction
• b.Into alternating hot and cold aisles✓
• c.Back to back with no aisle
• d.In a ring around a floor fan

The criterion says equipment should be arranged into hot and cold aisles when more advanced cooling schemes are not used. Racks all facing one way blow exhaust into the next row's intakes, back-to-back racks without an aisle block service access, and a floor fan is not a cooling design.UFC 3-580-01 (2024), para. 2-3.1.3.4 (room climate control)

Which rack equipment does the federal criterion say to bond to the rack bonding busbar?

• a.Only the patch panels, never the switches
• b.Every device, by drilling through its case
• c.Only those with a maker's bonding connection✓
• d.Nothing; racks are bonded, equipment is not

The criterion says to bond only appliances that have manufacturer bonding connections available. Drilling cases is not an approved method, limiting bonding to patch panels is arbitrary, and equipment with a bonding point should be bonded along with the rack.UFC 3-580-01 (2024), para. 2-4.3 (rack bonding)

What does the federal cabling specification require before fastening conductors to a bonding busbar?

• a.Clean it and apply anti-oxidant✓
• b.Paint the busbar to prevent corrosion
• c.Sand the conductor insulation smooth
• d.Wrap the lug in electrical tape

The busbar is cleaned and an anti-oxidant is applied to the contact area to control corrosion and reduce contact resistance. Paint and tape insulate the very contact that must conduct, and sanding insulation does nothing for the connection.UFGS 27 10 00 (2025), para. 3.7 (telecommunications bonding)

An unpowered amplifier enclosure at a satellite installation connects only to a coaxial cable. When is the enclosure considered grounded under the safety order?

• a.If the coax shield is grounded✓
• b.When the coax is plenum rated
• c.Not until it has its own ground rod
• d.When it is mounted on a wooden wall

Unpowered equipment and enclosures are considered grounded where connected to an attached coaxial cable with an effectively grounded metallic shield. A separate ground rod is not required in that case, the mounting surface does not matter, and a plenum rating is about fire, not grounding.Cal. Code Regs. tit. 8 §2587.5 (grounding)

A camera must look out through a window. How should it be mounted, per the federal security criterion?

• a.With the room lights on behind it
• b.Angled to see its own reflection for alignment
• c.With the lens positioned close to the glass✓
• d.As far back from the glass as possible

The criterion says that behind glass the lens should be close to the glass, or reflections of the camera and background appear in the image. Mounting far back, angling toward the reflection, or lighting the room behind the camera all increase reflections.UFC 4-021-02 (2025), para. 5-2.3 (outdoor cameras)

An outdoor camera's scene includes a large area of sky, and the ground looks too dark. What does the federal security criterion advise?

• a.Mount higher to show less sky✓
• b.Add more sky to balance the exposure
• c.Point the camera at the rising sun
• d.Remove the auto-iris lens

Too much sky makes the camera expose for the bright sky so the ground appears dark; the criterion advises avoiding too much sky, for example by mounting the camera high. More sky worsens it, direct sun can damage the sensor, and outdoor cameras should always use auto-iris lenses.UFC 4-021-02 (2025), para. 5-2.3 (outdoor cameras)

A camera is lit at night by infrared illuminators. What does the federal security criterion say about its image?

• a.It keeps its IR-cut filter in place
• b.It will show color better than in daylight
• c.It cannot show color under IR light✓
• d.It cannot record under IR light

Cameras will not render color under IR illumination, so dual-mode cameras switch to monochrome and remove the IR filter. Color does not improve under IR, the filter must be removed for night operation, and cameras do record under IR — in black and white.UFC 4-021-02 (2025), para. 5-4.2 (infrared illuminators)

What is the difference between an electric lock and an electric strike?

• a.A lock moves its bolt; a strike retracts instead✓
• b.A lock can be fail-secure; a strike cannot
• c.An electric strike moves the bolt; a lock releases the keeper
• d.Both move the bolt; the strike is fail-safe

In an electric lock the bolt moves; in an electric-strike door the bolt stays stationary and the strike is retracted. The reversed statement is wrong, and both electric locks and electric strikes can be configured fail-safe or fail-secure.UFC 4-021-02 (2025), para. 4-6.10.2 (electric strikes)

An intrusion detection panel enclosure will be installed in a hallway. What does the federal security criterion require on it?

• a.A tamper switch that detects any opening✓
• b.A label listing the access codes
• c.A mechanical lock, with no switch
• d.A clear window to view the panel

Each intrusion panel and enclosure must be equipped with a tamper switch to detect opening, and tamper alarms must be annunciated. A viewing window or a code label weakens security, and a lock alone does not report an opening.UFC 4-021-02 (2025), para. 3-5.8 (tamper switches)

A camera records 15 frames per second with an average frame of 40 kilobytes. Using the federal security criterion's overhead factor, what bandwidth is needed?

• a.2,100 kilobytes per second
• b.56 kilobytes per second
• c.600 kilobytes per second
• d.About 840 kilobytes per second✓

Bandwidth equals the network overhead factor (typically 1.4) times frame rate times average frame size: 1.4 × 15 × 40 = 840 KB/s. Six hundred KB/s omits the overhead factor, 56 KB/s multiplies 1.4 by 40 only, and 2,100 KB/s uses an overhead factor of 3.5.UFC 4-021-02 (2025), para. 5-8.1 (bandwidth calculations)

Which standard defines the BACnet protocol, according to the federal HVAC controls specification?

• a.TIA-568
• b.IEEE 802.3
• c.NFPA 72
• d.ASHRAE 135✓

The specification defines BACnet as the communication requirements of ASHRAE 135. TIA-568 covers cabling, NFPA 72 covers fire alarm and signaling, and IEEE 802.3 covers Ethernet and PoE.UFGS 23 09 00, Instrumentation and Control for HVAC (definitions)

A fan status contact reports only "on" or "off" to a controller. What kind of point is it?

• a.An analog output
• b.An analog input
• c.A pulse accumulator output
• d.A binary input✓

A binary signal is a two-state signal, on or off, so a status contact read by the controller is a binary input. Analog points carry continuously varying values, an output is sent by the controller rather than read by it, and a pulse accumulator counts pulses.UFGS 23 09 00, Instrumentation and Control for HVAC (definitions)

What does network address translation (NAT) do on a VoIP network, per NIST?

• a.Gives each phone its own public address
• b.Reduces one-way latency below 150 ms
• c.Lets several devices share one public IP✓
• d.Encrypts the voice packets end to end

NIST describes NAT as hiding internal addresses and letting several endpoints in a LAN use the same external IP address — while making incoming calls more complex. It does the opposite of giving each phone a public address, it is not encryption, and it does not reduce latency.NIST SP 800-58, Security Considerations for VoIP Systems

What bit rate does NIST give for telephone audio encoded with G.711?

• a.8 kbps
• b.1 Mbps
• c.64 kbps✓
• d.150 kbps

NIST describes G.711 as an international standard for encoding telephone audio on a 64 kbps stream. Eight kbps is the G.729A compressed rate, 1 Mbps is far more than a voice stream, and 150 relates to the 150 ms latency bound, not bit rate.NIST SP 800-58, Security Considerations for VoIP Systems

An office moves its IP phones between floors and buildings freely. What emergency-calling concern does NIST raise?

• a.VoIP phones need battery power to dial 911
• b.911 calls cannot be placed over VoIP
• c.E-911 automatic location may be unavailable✓
• d.E-911 requires an analog fax line

NIST notes that E-911 automatic location service is not available with VoIP in some cases, because a number is not tied to a physical location. VoIP can place 911 calls, battery power is unrelated to dialing, and E-911 is not limited to fax lines.NIST SP 800-58, Security Considerations for VoIP Systems