Also, many systems use motion sensors that compute the proximity
of a room’s walls by producing infrared beams and measuring the time required for them to bounce back; if a beam comes back sooner than expected, it likely bounced off of a person
and the sensor registers motion. The control center keeps track of the status of the sensors and reports activity through LCD displays and other output devices. Moreover, when activity takes places, such as the opening of a window, the sensors report the activity to the control center and the center registers that a disturbance has occurred. In managed alarm systems, the control panel also checks the sensors to verify that they are still operational; if a sensor fails to reply, the center alerts the home owner of an out of order sensor. If the home owner activates the alarm system and the control center registers activity in the home, a signal is sent by the control to a buzzer, flashing lights or any other audiovisual alarm element. Our design for a functional keypad was the usage of an alternation of ports between inputs and outputs which is done by using the TRIS function.