Select one of the secondary digital inputs from the Digital Inputs Setup menu to open the Select Input Type configuration popup. You can select the operating mode and polarity for this digital input resource. The selection between active-high and active-low mode for the digital inputs is a global hardware configuration setting. You can use the configuration slide switch (S5) on the controller module to change the setting. See the HMS1655 Wiring and Installation Guide for complete details on configuring the digital input hardware resources.
You can configure the secondary digital inputs for one of four types, or you can disable them if not required. Occupancy Switch mode configures the selected digital input to automatically switch the operating mode to Occupied if not already selected. You can use the Zone Presence Sensor, or any other occupancy sensor, for this mode. Emergency Purge mode configures the selected digital input to activate the emergency purge mode, which forces the exhaust damper to the maximum open position. This is for emergency situations where a spillage occurs within the workspace at the fume hood. You can use the Override Switch mode to override the fume hood controller with the selected digital input, force the exhaust damper to the closed position, and mute the audible alarms. Flow Switch mode configures the selected digital input to convey the existence of actual air flow in the exhaust valve. Select one of the four active modes as the input type for the digital input, input polarity (normally-open or normally-closed) and the delay associated with the input activation.