Monitoring can use two video recorders. The monitoring system can use two video recorders. This configuration is often referred to as dual-machine backup or dual-record system. By using two video recorders, video backup can be realized while monitoring cameras, and the stability and security of the monitoring system can be improved. Monitoring refers to the behavior or system of continuously observing and recording people, things, places or events. It uses various technical means, such as cameras, sensors, recording equipment and related software and hardware equipment.