From 5s to 20s, as it seems it could take much more to complete and
get a response, as seen in the logs below.
<debug> [1568553228.546862] (ttyUSB3): --> 'AT+CNSMOD=1<CR>'
<debug> [1568553233.799470] (ttyUSB3): --> 'AT+AUTOCSQ=1,1<CR>'
<debug> [1568553238.798866] (ttyUSB3) setting up 3GPP unsolicited registration messages handlers
<debug> [1568553238.798932] (ttyUSB2) setting up 3GPP unsolicited registration messages handlers
<debug> [1568553238.798990] (ttyUSB3) device open count is 1 (close)
<warn> [1568553238.799029] (tty/ttyUSB3) at port timed out 2 consecutive times
<debug> [1568553238.799094] (ttyUSB3) device open count is 2 (open)
<debug> [1568553238.799148] (ttyUSB3): --> 'AT+CREG=2<CR>'
<warn> [1568553241.798727] (tty/ttyUSB3) at port timed out 3 consecutive times
<debug> [1568553241.798799] (ttyUSB3): --> 'AT+CREG=1<CR>'
<debug> [1568553244.795389] Enabling unsolicited registration events in primary port failed: 'AT sequence failed'
<debug> [1568553244.795462] (ttyUSB2) device open count is 2 (open)
<debug> [1568553244.795507] (ttyUSB3) device open count is 1 (close)
<warn> [1568553244.795545] (tty/ttyUSB3) at port timed out 4 consecutive times
<debug> [1568553244.795588] (ttyUSB2): --> 'AT+CREG=2<CR>'
<debug> [1568553244.800815] (ttyUSB3): <-- '<CR><LF>OK<CR><LF><CR><LF>OK<CR><LF>'
<debug> [1568553244.801624] (ttyUSB3): <-- '<CR><LF>OK<CR><LF><CR><LF>OK<CR><LF>'
<debug> [1568553244.808710] (ttyUSB2): <-- '<CR><LF>OK<CR><LF>'
abede5b9e3