What is Digital I/O?
Digital I/O stands for Digital Input and Output. Digital Inputs allow a microcontroller to detect logic states, and Digital Outputs allow a microcontroller to output logic states. Each digital I/O can be individually configured to one of 3 states: input, output-high, or output-low.
When a device inputs a high or low voltage level, DI will detect the changes and automatically send out SMS or email. DO can be in the control of SMS and outputs a high or low voltage level.