This a the simplified circuit which can be used in a hospital to notify a nurse or doctor if a patient needs help. The power supply powers a sound sensor which is linked to a light which turns on when activates. The nurse or doctor will then see the light and offer medical attention/aid.
The original more complicated circuit consists of two power sources which are regulated by two switches. This links to two inputs which can be activated by touch for more able patients and sound for less able patients. These link to two lights of which one flashes and one is a solid light so nurses can tell the difference.