• The system, if it operates nonstop, is unavailable for 0.85 hours per week. If availability drops by 5 percent, 9.24 hours per week are lost.

• The main switches in the Terra system are VSAT dishes on roofs of 221 remote locations, the host computer, and the hub stations.

• If Terra opens a new store, distribution center, or office, the new location can be added to the network by entering its address in the host and nearest hub station, and installing a satellite dish at the new location. If the old network were still in place, new cable or wire would have to be installed, at considerable cost.

---

• A credit card authorization can be efficiently handled.

• An electronic mail message can be efficiently handled.

• Digital voice for 1 second cannot be effectiently handled.

• Full-motion video cannot be handled.

• If Terra operated a terrestrial network that transmited data at 9.6 kbps, credit card authorization would be the only kind of message that could be handled.

---

• What are the 3 important characteristics of a perodic signal?

  There are several, but here are three. Others may be spectrum, bandwidth, and time period.

  • Amplitude

  • Frequency

  • Wavelength

• What is the relationship between a signal's spectrum and its bandwidth?

  The spectrum of a signal is the range of frequencies contained in the signal. The bandwidth is the difference between the lowest and highest frequency in the spectrum. It is therefore the width of the spectrum and is a measure of the information carrying capacity of the signal.

• The frequency of a digital signal is 2000Hz. What is its information capacity in bits per second?

  Frequency of 2000Hz implies a time period of 1/2000 secs , i.e., .5ms. In each time period, a digital signal can signal two bits (look at a figure that illustrates a digital signal). This implies that one bit is signalled every .25ms (i.e., half a time period). This is equivalent to 4000 bps (i.e.,1/.25ms).

Go back to the Course page