Many YSEM 520 EG1 units now have a QR code on the housing. Scanning it redirects to a live PDF of the manual.
If you check the device or manual again and share the correct model (e.g., YSEM 520-EG1, YS-EM520, or another brand like BK Precision, Fluke, Omega, etc.), I can help find relevant information or write a generic but professional equipment manual article for a similar class of device. ysem 520 eg1 manual
Install 4 x AA alkaline batteries into the compartment on the rear of the door. The factory default code is typically Opening & Closing Many YSEM 520 EG1 units now have a QR code on the housing