title: CREG, CGREG, CEREG AT commands
body: <p>I have to control a modem Cinterion ELS61 with a host application. Can anyone tell me in simple words which is the real difference among at+creg?, at+cgreg? and at+cereg? commands?
  I know that cgreg is related to 2G and 3G radio access technology and cereg with 4G/LTE one, but the actual differences are not so clear and neither the relation with the creg command results.
  It follows an example from a real case:</p>
  <pre><code>AT+CREG?
  +CREG: 2,5,&quot;38AD&quot;,&quot;02531900&quot;,7
  OK
  AT+CGREG?
  +CGREG: 2,4
  OK
  AT+CEREG?
  +CEREG: 2,5,&quot;2AF2&quot;,&quot;02531900&quot;,7
  OK
  </code></pre>
  <p>What is the difference among the answers to +creg and +cereg? Aren't they quite the same? And by the way, what does it mean that the same cell (02531900) has 2 difference location area codes (i.e. 38AD and 2AF2)?
  Thanks for the attention</p>