https://download.discomp.cz/Grandstream/Datasheets/Datasheet_GRP2601_English.pdf
Datasheethttps://download.discomp.cz/Grandstream/QIG/GRP-2601-QIG-1.pdf
Quick Installation Guidehttps://download.discomp.cz/Grandstream/User%20Guide/GRP260x-Series-Administration-Guide.pdf
Administration Guidehttps://download.discomp.cz/Grandstream/User%20Guide/GRP260x-Series-User-Guide.pdf
User Guide