[Problem]: The RTU5023's alarm dialing ringing time is too short to receive an alarm call. (Note: The general ringing time is 20S)
[Solution]: Make sure that the ringing must be answered by someone. You can set it to “Always dial when the alarm is dialed, until somebody press the # or * button on the phone to end the dialing”, using the SMS command 1234CON#. (Note: 1234 is the initial password of the device. If you change the password, you need to use the new password to send the command. For details, see page 13 of the manual.