Computer Science 825
                         Quiz 3              Name _______________________


1. What is the name of the modulation technique that is used to transmit
   an analog signal on a digital line.



2. Suppose a new  "high fidelity" voice telephone service has a bit rate
   of 2 ** 20 (1M)  bits per second. Each sample is digitized at a resolution
   of 2 ** 16 = 64K discrete levels.  What is the maximum frequency that
   can be carried by this channel?





3. Select the most suitable multiplexing scheme (FDM, ATDM, STDM) for each
   of the following cases:

   a. Digital channels with very unbalanced loads.


   b. Analog channels.


   c. Digital channels with very well balanced loads.


4. The main advantage of using a multiplexor to attach a remote cluster of
   ASCII terminals to a Unix machine is that it reduces the required number of

   a. Computer ports            c. Ports and Phone lines.

   b. Phone lines.              d. Ports, phone lines and terminals.


5. The main reason digital channels have much lower error rates than analog
   when used over long distances is:

   a. Digital signalling is more       c. Digital signals are amplified
      powerful than analog.               rather than regenerated.

   b. Digital signals are regenerated  d. Digital channels have much higher
      rather than amplified.              SNR's than analog.

6. Answer the following T or F.


   ___ a. One difference between IBM mainframe style terminals and VT100
          style ASCII terminals is that the IBM terminals only transmit
          when the enter key is hit while the ASCII terminals transmit
          each keystroke individually.

   ___ b. Computer systems of equal power will generally support more
          VT100/ASCII style terminals than IBM style terminals because
          the IBM style terminals require more CPU resources.

   ___ c. It is possible to attach multiple IBM style terminals using
          a single phone line AND a single port.