Service engineers are on call 24 hours a day; After receiving the customer's demand, complete the pretreatment within 4 hours and reply to the customer's solution in time. When on-site service is needed, the service personnel will arrive at the customer's location within 24 hours, and in remote areas within 48 hours. The service engineer cannot leave the site before the fault is handled, and the customer's permission is required to leave the site.