irtual reality will also be used for applications such as training, education, and commerce. APPENDIX A Comparison between Analog and Digital Signaling Speed or frequency on analog service is stated in hertz (Hz). A wavelength that oscillates, or swings back and forth between cycles, 10 times per second has a speed of 10Hz or cycles per second. A cycle starts at a neutral place in the wavelength, ascends to its highest point, descends to its lowest point, and then goes back to neutral. Lower frequencies are made up of longer wavelengths than higher frequencies. Analog telephone signals are analogous to water flowing through a pipe. Rushing water loses force as it travels through a pipe. The farther it travels in the pipe, the more force it loses, and the weaker it becomes. The advantages of digital signals are that they enable the following: Greater capacity The ability to mix voice, video, photographs, and e- mail on the same transmission enables networks to transmit more data. www.TechnicalPDF.com Higher speeds It is faster to re-create binary digital ones and zeros than more complex analog wavelengths. Clearer video and audio In contrast to analog service, noise is clearly different from on and off bits, and therefore can be eliminated rather than boosted along with the signal. Fewer errors Digital bits are less complex to re-create than analog signals. More reliability Less equipment is required to boost signals that travel longer distances without weakening. Thus, there is less equipment to maintain. Table 1-4 Compression Standards and Descriptions Compression Standard Description An International Telecommunications Union (ITU) standard used widely for video conferencing systems on LANs (local area networks) and WANs (wide area networks). A family of standards for voice encoding adopted by the ITU. It is used mainly on carrier networks to reduce the capacity needed for VoIP (Voice over IP). In-band, on-channel broadcasting that uses airwaves within the AM and FM spectrum to broadcast digital programming. IBO