There are two components to
the alarm, a transmitter remote and the receiver module in the car.
The remote module is for the user to carry with them once they have left
the car. The receiver device in the
car controls the responses to the signals emitted from the remote and handles
the response when the alarm is tripped.
The remote module will transmit different data packets to the receiver module, depending on one of three buttons, which could be pressed. The first button is the arm button which enables the alarm. The second is the disable button which disables the alarm and the panic button. The third is the panic button which triggers the hazard lights to go off and the horn to honk repeatedly.
The local module, situated
within the car, will receive this data packet from the remote module, and then
perform the appropriate action. The local module is connected to the car horn,
the hazard lights and a relay that connects the starter to the ignition.
Depending on the action requested by the remote module the local module will
configure the appropriate connection.
To activate the alarm, we used the switch that triggers the light inside the car to turn on when the car door is opened. When the alarm is armed, a relay that connects the starter to the ignition is tripped. When the person wants to drive the car again, they just disable the alarm and the relay reconnects the starter. When the alarm is tripped, the hazard lights will flash and the car horn will go off at approximately .25-second intervals.