title: ratio of bits/hz of digitized voice channel
body: <blockquote>
    <p>We need to transmit 100 digitized voice channels using a passband
    channel of 30 KHz. What should be the ratio of bits/Hz if we use no
    guard band?</p>
  </blockquote>
  
  <p>What I understand and get the bandwidth are :</p>
  
  <p><strong>30 KHz / 100 = 300 Hz</strong></p>
  
  <p>And the ratio of bit/Hz if no guard band is <strong>640000/300 = 213.333... bits/Hz</strong>
  (because digitized voice channel has a date rate of 64 Kbps) </p>
  
  <p>Is that right answers?</p>