These are available in 8 or 16 input or output point sizes. They attach directly to the right hand end of the Base Unit or Expansion Unit (see Digital Expansion Units below) which also provides them with power. Input blocks are opto-isolated, 24Vdc sink or source selectable to suit NPN or PNP sensors, and output blocks are available with relay or transistor outputs. The number of blocks that may be added depends on a number of factors. However, as a guide, with the FX1N, blocks up to 32 I/O can be added. Further expansion (of FX1N and FX2N) is achieved by adding an Expansion Unit (see 2 below), which in turn can be further expanded by adding more Expansion Blocks. With the FX2N, the number of I/O that can be added depends on the size of the Base Unit. For 16 and 32 I/O FX2N base units and 32 I/O Expansion units, up to 32 inputs, or 24 outputs, or (for example) 24 inputs and 8 outputs can be added. For larger Base and Expansion Units, up to 64 inputs, or 48 outputs, or (for example) 32 inputs and 24 outputs can be added. For full configuration details and limitations, please refer to the FX1N and FX2N Hardware Manuals.