Draytek Vigor3900 User Manual page 103

Or,
Available parameters are listed as follows:
Item
3G/4G PPP
Vigor3900 Series User's Guide
Description
SIM PIN code -Type PIN code of the SIM card that will be
used to access Internet.
Modem Initial String 1-Such value is used to initialize USB
modem. Please use the default value. If you have any
question, please contact to your ISP.
Modem Initial String 2-The initial string 1 is shared with
APN. In some cases, user may need another initial AT
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