Campbell Scientific NL240 Wireless Network Link Interface - Manual (Page 67)

Appendix C. NL240 Settings
TLS Certificate
Specifies the public certificate (in PEM format) for the encryption stack.
This setting can only be edited/transmitted if the DevConfig link
is considered secure (USB or TLS). If the TLS stack has been
initialized, the device will automatically negotiate a secure TLS
connection with DevConfig if the Use TCP option is selected.
NOTE
C-17