Read in analog signals and then send them back out slightly modified with 12-bit precision. That is what your Analog Signal Simulator was built for.
There is an LED for the power indicator and another for general purpose use. The switches are optional. Switch 1 is momentary normally open and switch 2 is a latching toggle switch. The intent is that the board would fit a few different needs with one single hardware design. Diversity is added through software.
The board is built for a Serpac CH8 enclosure. Analog signals are kept at the top near the input to the board so that the traces are as short as possible. The voltage regulator / power input is on the right side of the board. The processor is at the bottom with the SPI bus kept on the left side.