Parking brake alarm systems

A parking brake state detection circuit for use in a transportation vehicle, comprising:

• a first relay including a first relay switch that closes when an ignition of the transportation vehicle is turned off;
• and
• a second relay including a second relay switch that is coupled to the first relay switch and that closes when a parking brake of the transportation vehicle is disengaged;
• wherein the first relay switch and the second relay switch to be disposed in series between an operator warning interface system and ground to form a breakable conductive path between the operator warning interface system and the ground, the first relay switch and the second relay switch to form at least a portion of an unbroken conductive path between the operator warning interface system and the ground when the first relay switch and the second relay switch are closed, the operator warning interface system to generate an audio and/or visual alert to indicate that the parking brake of the transportation vehicle is disengaged when the operator warning interface system is provided with the unbroken conductive path to the ground.

A parking brake state detection circuit for use in a transportation vehicle, comprising:

• a first node to couple to ground;
• a second node to couple to cathode of a battery;
• a third node to couple to an operator warning interface system that, when prompted, provides an audio and/or visual indicator for indicating that a parking brake of the transportation vehicle is disengaged;
• and
• a relay switch to conductively link the third node to the first node when the parking brake of the vehicle is not set and to conductively link the third node to the second node when the parking brake of the transportation vehicle is actuated,
• wherein the relay switch is part of a relay that further includes a coil, wherein when an electrical current flows through the coil the relay switch will conductively link the third node to the first node and when no electrical current is flowing through the coil, the relay switch will conductively link the third node to the second node, the coil having a first terminal and a second terminal, the first terminal coupled to a battery and the second terminal coupled to a switch, where the switch to be open when the parking brake is actuated, and to be closed when the parking brake is disengaged, and when the switch is closed, the switch links the second terminal of the coil to the ground.