If you have `AT+GTUSBMODE=40` (0e8d:7126) then the AT-command port is ttyUSB2 and with `AT+GTUSBMODE=41` (0e8d:7127) the AT-command port is ttyUSB4.
In `AT+GTUSBMODE=40` (0e8d:7126) then the AT-command port is USB interface 4 and in `AT+GTUSBMODE=41` (0e8d:7127) the AT-command port is USB interface 6.
If you don´t have any other seial USB interfaces connected it will be `/dev/ttyUSB2` and `/dev/ttyUSB4`.
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If the script doesn´t work, check in syslog. If it stops at ` offline -> registered - .....` then your service provider doesn´t use NITZ and disconnections can´t be detected. You can use `atc-fib-fm350_gl_2024-04-24-0.2_all.ipk` instead, but you have to check network connectivity by your self.