Potentially silly question 😅

Hi! I'm a FTM, and have no clue about these things. Do OB offices usually have their own in-house ultrasound techs and machines, or are you normally directed to an imaging lab at a hospital?

My doctor made it sound like they had one in-house, but is now telling me I'll be going to the hospital I'll be giving birth at. Initially I was mad but it occurred to me maybe she just thought I knew how it worked. So... is it normal to be sent off site for your ultrasounds, or do they usually do them in their office?

Edit: Thanks ladies! Now I know to ask how they go about things with ultrasounds tomorrow when I see my OB again. 💖