The dual-power supply mode mainly involves the switching and utilization of two independent power sources to ensure the continuity and reliability of power supply. This power supply mode is widely used in places with high power requirements, such as important party, government, and military agencies, key national defense and scientific research projects, as well as important news, broadcasting centers, transportation and communication hubs, etc.
The dual-power supply mode mainly includes the following types: 
Self-switching and self-recovery mode: In this mode, when the main power supply is operating normally, the system is powered by the main power supply. Once the main power supply fails, the system will automatically switch to the backup power supply for power. When the main power supply returns to normal, the system will automatically switch back to the main power supply for power. 
Self-deployment without self-recovery mode: This mode is further divided into self-deployment without self-recovery and relative self-deployment without self-recovery. In the self-deployment without self-recovery mode, when the main power fails and switches to the backup power, even if the main power returns to normal, the system will not automatically switch back to the main power. While in the relative self-deployment without self-recovery mode, although the system does not automatically switch back to the main power, under specific conditions, such as when the backup power is low or when the main power supply needs to be restored, the switch can be achieved through manual operation. 
Alternate power mode: In this mode, when the main power fails, the system will automatically switch to the backup power supply. At this point, the backup power becomes the primary power, and the original primary power becomes the backup power. When the original primary power resumes power supply, the system will not automatically return to it but will maintain the current primary-backup relationship. If the new primary power (the original backup power) fails, the system will automatically switch to the new backup power (the original primary power) for power supply. 
The selection of the dual-power supply mode should be based on actual needs and scenarios to ensure the reliability and continuity of power supply.