Computer Science 825
                         Quiz 2              Name _______________________

1. a. How many signalling levels must be used to transmit 64,000 bits
      per second on a noise free channel that has a bandwidth of 4000hz.
      (Show work for partial credit).







   b. What signal to noise ratio (in db (not sp/np)) is necessary to
      achieve the 64,000 bit per second data rate on the 4000 hz channel.








2. a. The general form of a modulated sine wave carrier is
      f(t) = A sin (Wt + H).  Which of the three parameters
      is varied in frequency modulation?



   b. Which modulation scheme does the standard 1200 b.p.s modem
      employ?



   c. At what baud rate does the standard 1200 b.p.s modem signal?



3. Answer the following T or F:


   ___ a. All phase modulation schemes result in self clocking signals.


   ___ b. It is possible to define a self clocking signalling scheme
          that uses pure frequency modulation.

   ___ c. The only way to signal on a digital channel is with a baseband
          (on/off) signal.

   ___ d. The main difference between synchronous and asynchronous channels
          is that with asynchronous channels there is no requirement
          that sender and receiver have clocks that must run at the
          same speed.

4. What fundamental difference between digital and analog channels
   enables digital channels to  provide far superior performance over
   VERY LONG distances.