Hello,
Indeed, if predefined values are acceptable, then the best solution will most likely be to call Modbus Write function via the Custom Script functionality. Syntax for writing data to Modbus registers via a command can be found here: Rut 955 : Trying to read modbus rs485 data from slave device using Pyserial - #5 by AndzejJ
Let me know if there are any difficulties with the configuration.
EDIT: It seems like we’ve already had a similar question: RUT955 SMS utilities - Crowd Support Forum | Teltonika Networks
Best regards,