Water and salinity balances for irrigated agriculture in Pakistan

A PC card having automated Drag and Sleep function is equipped with Drag and Sleep control circuit to connect to the controller of the PC card, a connector unit and the other devices. As the connection of the connector unit to the external system (the external networks or devices) is cut off, the Drag and Sleep control circuit generates and transmits interrupt-signal to the controller to enable the PC card to get into sleep state; when the disconnected connector unit is once again connected to the external system (such as the external networks or devices), the Drag and Sleep control circuit generates and transmits interrupt-signal to the controller to enable the PC card to resume normal state, thus the PC card can effectively save energy because it can greatly lower the electric current consumption under the sleep state.