The assistant then stands in place against the board and gives an audible signal to commence the stunt.

The pedal can have a vigilance function built in, where drivers must release and re-press the pedal in response to an audible signal.

In such instances, an audible signal would sound and play was suspended at that point.

The problem was traced to the power supply of the equipment which converts the signal from the atomic clocks into an audible signal.

Usually the alarm panel's sounder will activate if a trouble condition exists, though older systems would sometimes activate a bell or other audible signal connected to the panel.