The Allen-Bradley 1756-IA8D is a ControlLogix Digital I/O module.

8 diagnostic inputs, with 4 points available per group, are in this AC input module. This module is suitable for a 1756 ControlLogix chassis and is only compatible with the 1756-TNBH or 1756-TBSH removable terminal block, or RTB.

A unique feature of the 1756-IA8D is the Field Power Loss detection. When field power loss occurs to the module or zero cross cannot be detected, a point level fault is then sent to the controller. This allows the controller to find the exact point faulted, so make sure to enable this option only for points that are in use. If points not in use have the Field Power Loss detection activated, these points will be registered as faults during the operation and not as points not in use.

Other configurable features of the 1756-IA8D include the Change of State, Input Filter Times, Open Wire Detection, Diagnostic Latching, and Diagnostic Change of State.

The nominal input voltage of this module is 120 Volts AC and 50 to 60 Hertz, same with its voltage category. The backplane current is 100 mA at 5.1 V DC and 3 mA at 24 V DC, and the total backplane power is at 0.58 W. Its operating voltage ranges from 79 to 132 V AC and 47 to 63 Hz. The current draw at 5.1 V is 100 mA and for 24 V, it is 3 mA. Maximum power dissipation is 4.5 W at 60 Degrees Celsius, while its maximum thermal dissipation is 15.35 BTU/hour. During an off-state, its maximum voltage is 20 V and the maximum current is 2.5 mA. The on-state current, on the other hand, ranges from 5 mA at 74 V AC to 16 mA at 132 V AC. This module has an input delay time from screw to backplane; from 'off' to 'on', the hardware delay is a maximum of 10 ms + filter time that is user-selectable (1 or 2 ms), while from 'on' to 'off', the hardware delay is a maximum of 8 ms + the user-selectable filter time (9 ms or 18 ms). The continuous isolation voltage of this module is 125 V.