The 1771-IQC input module is a digital input module manufactured by Allen-Bradley/Rockwell Automation in the PLC 5 series. This DC selectable input module operates on a voltage range of 5 to 30 Volts DC, and this module is an 8-point selectable input module. The Bulletin 1771 digital DC input modules like this one are designed and intended for converting DC signals from the user devices to the correct logic level for use by the processor. Some of the features of the typical input devices this series and the 1771-IQC module in particular include proximity switches, selector switches, limit switches, pushbutton switches, and float switches. The DC input modules come with a variety of input terminals per module and it is compatible with current chassis including the 1171-A1B, A2B, A3B A3B1, A4B, AM1, and AM2 chassis. It features 8 input image bits and it is compatible with the ½ slot, 1-slot, and 2-slot addressing.

The Allen-Bradley 1771-IQC digital input module has the input filtering feature that helps to limit the effect of voltage transients that is caused by electronic noise or contact bounces. Without filtering, the voltage transients may produce false data. Other components of the 1771-IQC module that are protected from possible damage by electrical transients by the opto-electrical isolation include the module logic circuits, backplane circuits, and the entire system. However, some modules in the Bulletin 1771 product line allow the users to set the input filter time jumpers depending on specific module specifications. Additionally, this module is compatible with the superseded chassis line, including the 1771-A1, 1771-A2, and 1771-A4 chassis. Nevertheless, it does not require conditional module placement.