GPRS AT Command CGDCONT - Do I really need an APN? <p>I am developing embedded firmware to communicate with the Multi-Tech's MTSMC-H5 GPRS Modem. I am unclear the use of AT+CGDCONT command. In the H5 modem's Reference Guide, it states the command format is</p> <pre><code>&gt;AT+CGDCONT=[&lt;cid&gt;[,&lt;PDP_type&gt;[,&lt;APN&gt;[,&lt;PDP_addr&gt;[,&lt;d_comp&gt; &gt;[,&lt;h_comp&gt;[,&lt;pd1&gt;[,…[,pdN]]]]]]]]] &gt;... &gt;&lt;APN&gt; Access Point Name. String parameter that is a logical name used to select the &gt;GGSN or the external packet data network. If the value is empty (“”) or omitted, &gt;3GPP TS 27.007 AT COMMANDS then the subscription value is requested. &gt;... </code></pre> <p>What effect would that be if I leave the APN field blank? It seems I can connect to the cell network while leaving the APN field blank. I tried several SIM cards and they all seem to work without specifying the APN field. However, I'd like to know for sure that what I do is appropriate. Because I have very limited UI capability (no real keypad on the device that the modem is attached to), it is highly desirable if an end user does not have to enter any APN information.</p>