When the animal comes up to the Nofence boundary, the collar emits an audio warning. The signal resembles a scale of tones, and starts at a low pitch and rises gradually as long as the animal is outside the Nofence boundary. The animal will recognise this tone scale, turn, and go back to the Nofence pasture to avoid the electric pulse.
The illustration shows normal behaviour when the animal moves out of the Nofence pasture: it responds to the audio warning, turns, and goes back into the Nofence pasture.
The electric pulse will only be emitted if the collar has played all the tones in the audio warning. This is because the signal should be recognisable and predictable for the animal. It takes a minimum of 5 seconds and maximum of 20 seconds to play the full scale. The scope of the warning field depends on the speed of the animal as it leaves the Nofence pasture, but in the majority of cases this will be approximately 3 metres.
To turn the audio warning off and avoid the electric pulse, the animal must turn around and go back to the Nofence pasture.