The Allen-Bradley 1771-IA2 is a PLC 5 Digital AC/DC Input Module. It converts AC signals provided by user devices to the logic level needed by the processor. It directly controls the state of corresponding bits in the PLC data table. It contains various input devices such as pushbuttons, limit switches, pilot lights, motor starters, and annunciators to interface with on/off sensors and actuators. It provides a modular design with space-saving and pocket-friendly means to add input to a PLC control system. It comes with a 1771-WA wiring arm to replace the module, eliminating the need to disconnect wiring. It is a series A module and supports ½, 1, and 2-slot I/O addressing. It has applications with AC/DC proximity switches.

The 1771-IA2 module has 8 inputs with a 120V AC/DC voltage category. It has an operating voltage range of 87 - 138V AC or 97 - 138V DC. It has a typical signal delay of 24ms (±10) at on/off AC state and 10ms (±4) at on and 20ms (±9) at off DC state. It has a maximum off-state current of 2.8mA and a backplane current load of 75mA. It has a maximum power dissipation of 10.7W and thermal dissipation of 36.5 BTU/hr. It is installed in a 1771 I/O chassis containing a PLC processor. Keying bands for putting it in the right slot are between pins 10 and 12 for the upper connector and between pins 4 and 6 for the lower connector.

The 1771-IA2 module has 8 orange status indicators for field-side indication at the front panel. It contains optoelectrical isolation to protect the system circuits from electrical transients. It also contains input filtering feature to reduce electrical noise.