Once you have identified the brand, use the following resources to find the schematic:

The CM4 is a system-on-module (SoM) that relocates the core power of a Raspberry Pi 4 into a compact form factor for industrial and custom hardware design. Compute Module hardware - Raspberry Pi Documentation

Level shifting and IO protections

Elias frowned. He didn't have a replacement opto-isolator of that specific vintage. He looked at the schematic again. The diagram showed the internal logic: an LED triggering a phototransistor. It was a simple switch. He didn't need the exact part; he just needed to replicate the isolation.