Дальнейшее описание: In a Tricon controller, the GATENB function block opens a gate for external-host read/writes to a specified range of Modbus aliased variables when the controller is operating in RUN mode. In a safety shutdown application, the keyswitch is typically set to RUN mode for normal operation. However, this mode does not support Modbus writes from external hosts. To solve this problem, TriStation 1131 provides gated-access function blocks to programmatically enable and disable external-host writes to a Tricon controller. GATENB allows you to specify a range of aliases for each of these data types:
• Discrete Read/Write
• Integer Read/Write
• Real Read/Write
You should use only one GATENB function block in a program. If you do not want to specify alias ranges for certain data types, leave their starting and ending values at zero (the default).

Нашла alias variable - переменная-псевдоним. Подходит ли это в данном контексте? А alias number - не указатель ли часом?