For what we call a standard calving you will receive 2 high activity warnings an hour apart approx 1.5 hours before the birth.
In some cases a farmer can receive false alerts and the most common reasons for these are as follows:
Being on the tail for longer than 4 days without a break.
Being too low down on the tail.
Other reasons why you may receive a false alarm:
Straw bedded shed getting new straw and cow with more activity than normal.
Another cow calving beside the cow with the sensor fitted.
Lice - the cow is consistently scratching.
Mastitis - in a severe case of infection.