74HC165 8-Bit Parallel-In Serial-Out Shift Register IC (DIP-16)

Where the 74HC595 lets a microcontroller drive many outputs from a few pins, the 74HC165 solves the opposite problem: reading eight separate digital inputs, such as switches or sensor trip points, while only using up a handful of pins to shift that data in serially. Several of these chips can be daisy-chained together to read dozens of inputs from the same few control lines, which is exactly how larger button panels, DIP switch banks, and multi-zone sensor arrays are commonly wired up without exhausting a microcontroller's limited GPIO. As a bare DIP-16 chip rather than a ready-made breakout, it suits builders who are either prototyping the wiring on a breadboard first or designing their own custom PCB around it.