[EricH]

You are correct. There is a sensor in the chute from the goal and another over the player station. When a ball comes in, a flag is set for a certain time (based on the formula). When a ball goes out, the next flag is cleared.

And the sensor in the chute (and probably in the return) is a quadrature-encoded photoelectric sensor. (Forget whether that's in Section 6, the field drawings, or the DOGMA document, but it's there.)