If there are no control signals from the remote control, the drone will hover at the current position if there is a good GPS signal. After a few seconds, which can usually be set, an emergency run programme starts. Modern systems also offer the option of automatically returning to the take-off site in the event of a radio failure. This emergency function usually ends with the descent and remains in place until the radio connection is re-established or the drone has landed. The emergency function "descend" or "return to take-off site and descend" also starts when the battery voltage is low.