The Signet Dual Relay Module works with the 8900 Multi-Parameter Controller. Relay modules are optional when building an 8900. Relay modes of operation include off, low, high, window, USP, totalizer volume, advanced, proportional pulse, pulse width modulation, volumetric pulse, % reject, % recovery and % passage. The advanced relay option For �AND/OR� logic is used For up to 3 conditions. For instance, a relay will go to high/low if �a� is true and �b� or �c� is false. One or two relay modules can be installed into the 8900. One additional external relay module can also be used at the same time (See optional external relay ordering information. ) All relays are assignable to any input channel. The Signet 8900 Multi-Parameter Controller takes the concept of modularity to the extreme. Each 8900 Controller is field-commissioned with the users-specified combination of inputs, outputs, and relays using simple-to-install modular boards into the base unit. To build a functional 8900 controller, choose the base unit (W2T127899), power module, and input/output (I/O) module. Configure the system by selecting either two, four, or six input channels which accepts any of the Signet sensors listed below, and/or other manufacturer's sensors via a 4 to 20 mA signal converter. To complete your unit, choose a power module with universal AC line voltage or 12 to 24 VDC. Links to the base unit and additional products can be found at the bottom of the page. For additional information about configuring the base unit, click the datasheet option above.