What does the circular sign with a red border indicate?

The sign shown in the image indicates the prohibition of passing without stopping. It indicates the point where stopping is mandatory due to the proximity, according to the inscription it contains, of a customs post, police checkpoint, toll booth, or other facility, and that mechanical stopping devices may be installed beyond them (travel may not be resumed until the requirement established by the sign has been complied with). This stop at the toll booth is usually to pay the fee for using the road. This sign may also be found at a customs post or a police checkpoint.