FMU130 Negative Input Usage Scenario
FMU130 device is the first "Teltonika" device that has a configurable input with a possibility to configure a negative input (ground sense).
Negative input (ground sense) purpose is to detect ground when it‘s connected. This allows much easier and safer installation of external accessories. There won‘t be needed to connect a power supply to external accessories that digital input could sense a change of a signal.
Animated picture below shows a simple example of negative input usage scenario. There are many alarm buttons, sensors and other accessories that operate on this principle: one alarm button pin is connected to ground (it could be connected to any ground, not necessarily to FMU130 device ground), other pin – to negative input. When the button is pressed, ground is connected and negative input detects it.