Progression: Field Tech IV - V

Baseband signaling - answer-is predominant in Ethernet networks. two ways we can use a flow of energy to carry data - answer-Analog and digital Simplex - answer-A signal may flow in only one direction. A commercial radio station uses simplex communication, because listeners cannot transmit radio signals back to the station. Half-duplex - answer-Signals may flow in either direction, but not simultaneously. For example, a two-way radio allows only one user to speak at any one time. Full-duplex - answer-Signals may flow in both directions simultaneously. A telephone is the best example of full-duplex communication. One wire brings a signal from the telephone company to your home, and a second wire carries a separate signal from your home back to the telephone company. Thus, you can both hear and speak simultaneously. Synchronous - answer-The communicating parties or endpoints use time to organize communication. In a data network, two communicating computers use each clock "tick" to detect whether a digital bit is a 1 or 0. For example, as each time interval passes, a computer checks the network cable to see whether the voltage is high (binary 1) or low (binary 0). Because the timing determines the meaning of the signal, it is essential that the endpoints are synchronized to the same clock before sending signals. Asynchronous - answer-Bits are not transmitted on any strict timetable. For example, a computer modem typically uses 8 bits to represent one character or letter. To indicate the start of each character, the sending modem transmits a "start" bit to alert the receiving end to the incoming signal. After the final bit of the eighth character is transmitted, the sending modem transmits a "stop" bit to indicate the end of the character. This process is repeated for each character the modem transmits. Thus, the receiving modem must stay synchronized to the signal only for the length of time it takes to transmit 8 bits. If the sending and receiving clocks are slightly out of synchronization, these short data transfers will still be successful.