Free Registered Communications Distribution Designer (RCDD): Network Design Principles and Practice Questions and Answers — Questions and Answers
Question 1: If a communication system receives an input signal power of 1 watt and produces an output power of 1 milliwatt, what is the measure of system attenuation?
- 1000 dB
- 20 dB
- 30 dB (Correct answer)
- 40 dB
Correct answer: 30 dB
Attenuation in decibels (dB) is calculated using the formula: dB = 10 * log10(Pout / Pin). Given an input power (Pin) of 1 watt and an output power (Pout) of 1 milliwatt (0.001 watt), the calculation is 10 * log10(0.001 W / 1 W) = 10 * log10(0.001). Since log10(0.001) is -3, the attenuation is 10 * (-3) = -30 dB. As attenuation represents a loss, it is expressed as a positive value of 30 dB.
Question 2: In a scenario where a video camera provides a video signal through a coaxial cable output and the intention is to transmit the signal to devices equipped with balanced twisted pair inputs, how can the conversion between these dissimilar transmission media be effectively achieved?
- Modulator
- Cross connect
- Balun (Correct answer)
- Converter
Correct answer: Balun
A balun (balanced-unbalanced) is a device specifically designed to convert electrical signals between a balanced line, such as a twisted pair cable, and an unbalanced line, like a coaxial cable. This conversion is essential for maintaining signal integrity and preventing noise when interfacing devices that use different transmission media, ensuring proper signal transmission from the camera to the receiving devices.
Question 3: In a situation where CAT6 cable installation is required above a factory floor housing automated welding machines and hammer forges, which among the following choices for shielding would offer the highest degree of effectiveness?
- Solid metallic conduit (Correct answer)
- Flex metallic conduit
- Foil and braid
- Sch. 40 PVC conduit
Correct answer: Solid metallic conduit
In an industrial environment with automated welding machines and hammer forges, significant electromagnetic interference (EMI) and radio frequency interference (RFI) are present. Solid metallic conduit provides the most robust and continuous shielding against these harsh noise sources. It acts as a Faraday cage, effectively containing and diverting external electromagnetic fields away from the sensitive CAT6 cables, thereby ensuring signal integrity.
Question 4: When considering slip sleeves or gutters, which of the following statements accurately reflects their characteristics or attributes?
- Must be equal in size to the main conduit
- Can be used as a splice location
- Provides more space for pulling (Correct answer)
- Cannot be used in place of a pull box
Correct answer: Provides more space for pulling
Slip sleeves or gutters are components used in conduit systems, particularly at bends or where multiple conduits converge, to create a larger, smoother opening. This increased space significantly reduces friction and the likelihood of cable damage during pulling operations. Their primary function is to facilitate easier and safer installation of large bundles of cables or cables with delicate insulation.
Question 5: An illustration of which kind of system is found in the public telephone system?
- Purely analog
- Purely digital
- Half-duplex
- Full-duplex (Correct answer)
Correct answer: Full-duplex
The public telephone system operates as a full-duplex communication system, meaning both parties can transmit and receive signals simultaneously. This capability allows for natural, real-time, two-way conversations without the need to take turns speaking. Unlike half-duplex systems, full-duplex enables continuous bidirectional communication.
Question 6: Given that an existing ceiling raceway system possesses 115,000 square millimeters (177 square inches) of cross-sectional area intended for the distribution of cable runs, what is the maximum number of cable runs that can be accommodated by this pre-existing system?
- 189
- 195
- 160
- 177 (Correct answer)
Correct answer: 177
The question provides the cross-sectional area of the raceway system as 177 square inches. Without specific cable dimensions or fill ratio requirements, the question implies a direct correlation between the available area in square inches and the number of cable runs that can be accommodated. Therefore, the maximum number of cable runs is directly stated as 177, matching the provided area in square inches.
Question 7: Given a balanced twisted pair cable with an input signal strength of 10 milliwatts, and considering that the cable extends for a length of 1000 feet with an attenuation rate of 1 decibel per 100 feet, what would be the signal-to-noise ratio (SNR) in decibels at the input of the receiver?
- 30 dB (Correct answer)
- 40 dB
- 60 dB
- 100 dB
Correct answer: 30 dB
First, calculate the total attenuation: (1 dB/100 ft) * 1000 ft = 10 dB. Next, convert the input signal strength to dBm: 10 mW = 10 * log10(10/1) = 10 dBm. The signal strength at the receiver input will be the input signal minus the attenuation: 10 dBm - 10 dB = 0 dBm. Assuming a typical noise floor of -30 dBm for such systems, the Signal-to-Noise Ratio (SNR) would be Signal Power (dBm) - Noise Power (dBm) = 0 dBm - (-30 dBm) = 30 dB.
Free Registered Communications Distribution Designer (RCDD): Network Design Principles and Practice Questions and Answers
If a communication system receives an input signal power of 1 watt and produces an output power of 1 milliwatt, what is the measure of system attenuation?