You need to have one second of silence before and after the +++ sequence.
Also less than 1 second of silence between each ‘+’.
For example the working case to switch to command mode:
ABC……+++…… (Here many dots means long time and more than 1 second)
ABC……+.+.+… (Here one dot means short time and less than 1 second)
For example the failure case which fails to switch to command mode. All the characters will be seen as data.
ABC+++…… ABC
ABC+++ABC
ABC……+++ABC
ABC……++++….ABC
ABC……++……+……ABC
ABC……+……+……+……ABC