| 1: | Give an example of how a computer might transmit binary 0s and 1s using variations in voltage on a wire. |
| A1: | Answer: The transmitting device could induce one voltage level on the wire to imply a binary 0 and a different voltage level to imply a binary 1. |
| 2: | Imagine that two computers are sending and receiving data over a wire. How often would the receiving device need to sample the electrical signal on the wire if the standard called for 20 bps transmission speed? |
| A2: | Answer: The receiving device would sample the signal 20 times in a single second, interpreting the signal as either a 0 or a 1. By doing so, it would receive 20 bits per second. The actual time interval would be 1/20 of a second, or .05 seconds. |
| 3: | As explained in the chapter, do computers usually transmit data over the same wires they use to receive data? Why or why not? |
| A3: | Answer: Computers use different wires for transmission and reception to avoid overlapping electrical signals. Overlapped electrical signals cause confusion, misinterpretation of the signals as meaning the wrong binary value, or the complete inability to interpret what binary value was meant by a particular electrical signal. |
| 4: | As explained in the chapter, do computers usually transmit data over a single wire, or do they use two wires? |
| A4: | Answer: Computers use a pair of wires, twisted together, for transmission. The twisted pair of wires reduces the impact of EMI. |
| 5: | How many wires can fit inside the end of an RJ-45 connector? |
| A5: | Answer: Eight |
| 6: | How many wires are needed for a PC to successfully send and receive data to another PC using an Ethernet LAN cable with RJ-45 connectors? |
| A6: | Answer: Four. Although the RJ-45 connector supports eight wires, the wires inserted in pin positions 1, 2, 3, and 6 are the ones Ethernet uses for data transmission and reception. |
| 7: | Explain why a straight-through LAN cable does not work when connecting two PCs directly, just using the cable. |
| A7: | Answer: Each PC's NIC sends data over the wires in pins 1 and 2. A straight-through cable terminates those wires in pins 1 and 2, respectively, on the other end of the cable. As a result, both NICs transmit data on wires 1 and 2, and neither NIC receives an electrical signal on pins 3 and 6. |
| 8: | Explain why a cross-over LAN cable does work when connecting two PCs directly, just using the cable. |
| A8: | Answer: Each PC's NIC sends data over the wires that use pins 1 and 2. A cross-over cable terminates those wires in pins 3 and 6, respectively, on the connector on the other end of the cable. When one device sends on pins 1 and 2, the other device receives that signal on pins 3 and 6, as expected. The same thing also occurs when the second device sends on pins 1 and 2. |
| 9: | Explain why a straight-through LAN cable works when connecting a PC to a hub. |
| A9: | Answer: The hub reverses its logic compared to a NIC, in terms of what pins are used for transmission and reception. The PC sends on pins 1 and 2, and the hub expects to receive data on pins 1 and 2, so the straight-through cable works. Similarly, the hub sends on pins 3 and 6, so that the NICs, which receive on pins 3 and 6, successfully receive the data. |
| 10: | What is the main difference between UTP and STP cabling? Which is more popular today? |
| A10: | Answer: Unshielded twisted-pair cabling does not add shielding against EM interference, whereas shielded twisted-pair cabling does. UTP is by far the more popular option today. |
| 11: | List some of the key benefits of a structured cabling plan. |
| A11: | Answer: A structured cabling plan helps to minimize the need for running new cables because you can easily determine the distance from each wall plate to the wiring panel. This allows the electrician to run a cable between each wall plate and the wiring closet, while allowing other workers to connect a patch cable to complete the wiring. |
| 12: | Imagine a hub with ten physical ports, and cables connecting each port to ten different PCs. The hub receives an electrical signal from the PC on port 1. Where does the hub forward the electrical signal? |
| A12: | Answer: The hub repeats the signal out ports 210. It does not repeat the signal out port 1 because that was the port in which it received the signal. |
| 13: | Define the term "pin" in relation to an RJ-45 connector. |
| A13: | Answer: A pin is the physical position in the end of a connector, where the copper part of a wire sits. |
