The answer seems to lie with the special signals that are given in feline 'language' by certain specific sounds.

Some alarms warn you when the batteries need changing by giving a special signal.

This sudden shift causes certain atoms in the patient's body to make special signals.

If you don't move every so often, a special signal goes out.

"We ought to have a special signal," he said as they handed him the basket and climbed through the window.

They sounded like a special signal, that could be heard on the fire tower.

This was the first and only time this special signal has been used.

There are also certain special signals given for unique incidents.

A part of the computer generates special electronic signals which cause the characters to be displayed on the screen.

A special signal was to be put into use for carriers during aircraft operations.