For real-time devices in Zentra, input settings can be configured “Normally Open” or “Normally Closed.” These settings are also known as “Active High” and “Active Low,” respectively. They apply to all input mechanisms supported by Zentra: Door Sense (Door Position Sensor, or DPS), REX, and AUX. These settings are determined by the physical wiring of your hardware, and are configured at the time of installation by the team responsible for the initial setup of the device. It is uncommon these settings need changed after initial installation and before making any changes you should discuss with your installation team. For reference, additional detail is included below.
“Active high” describes when the input should be triggered as the voltage changes from 0V to 5V (toggling the switch from closed to open). “Active low” describes when the input should be triggered as the voltage changes from 5V to 0V (toggling the switch from open to closed).
Active high is also known as normally closed and active low as normally open. “Normally closed” vs “normally open” describes what the expected “resting” or default state of the circuit is intended to be. The input of a normally closed circuit will be at 0V and when you open the circuit it will change to 5V which will trigger the input. The input of a normally open circuit will be at 5V and when you close the circuit it will change to 0V which will trigger the input.
Door sense by default is active high. When the door is closed the input will be at 0V, as the door is opened, the circuit is broken and the input will change to 5V. When the door closes, the circuit is completed and the input will return to 0V. This configuration also provides a failsafe mechanism, if the sensor is damaged or the wire is cut, the door will be seen as open.
