Hi, Yes you can. [URL] User port stacking support for up to six units and unique mixed mode stacking that allows stacking of S4048-ON with S4048T-ON to provide combination of 10G SFP+ and RJ45 ports in a stack.   Page 969 [URL]
To whom it may concern,   Does S4048-ON stack with S4048T-ON? is there any limitaion ?   Sincerely, Jessie  
S4048-ON Stacking with S4048T-ON?