Dual contact closure - requires customer-provided Normally Closed (NC) or Normally Open (NO) switch (e.g. door open/close, door locked/unlocked, smoke present or absent). Factory default is NC. Each of the two ports (channels) can be independently set to NC or NO. RJ-12 connection to the PX/PX2 PDU. No support for water sensor. Requires firmware PX1.4.1 or higher or PX2.1.5 or higher.