The Allen-Bradley/Spectrum 1756SC-IF8H HART analog I/O module requires a single slot and it features 8-channel I/O with three terminals per channel. The unit is part of the ControlLogix system and it features a current range of 0 to 20 milliAmps or 4 to 20 milliAmps
The Allen-Bradley 1756-RM is a ControlLogix enhanced redundancy module. It is part of the Programmable Automation Controller (PAC) which is used to implement controller redundancy
The 1756-OF4 is a ControlLogix Four (4) channel analog output module. This module has an output Voltage and Current signals with ranges of -/+ 10VDC and 4-20 mA signals respectively
The 1756-OB32 is a ControlLogix Discrete output module which operate at a voltage category of 12 / 24VDC. This module has Thirty-Two (32) channels with Two (2) groups of Eight (8) channels each