On the nRF9161 DK, there are a few analog switches that are used to connect and disconnect signals to control buttons, switches, and LEDs.
The analog switches control whether the LEDs, buttons, and switches are connected directly to the nRF9161 General-Purpose Input/Output (GPIO) or to an I/O expander. See I/O expander for more information. The switches are controlled by the interface MCU System on Chip (SoC), which contains Nordic Semiconductor firmware.
Figure 1. IO expander, LED, and button control
