I'm using a 2003-era external iSight "Autofocus Video Camera + Noise Suppression Microphone" with an Apple Cinema Display and USB-C MacBook Pro running macOS 10.15.
It's connected via a long succession of dongles:
iSight > FireWire 400 > Apple Cinema Display > FireWire 800 > Thunderbolt 2 > Thunderbolt 3
It still works great for video, if a bit low resolution, and you can't beat the design:
However, the iSight camera's microphone does not appear to be working. People cannot hear me when my laptop is in clamshell mode, despite being on video via the external iSight.
System Preferences > Sound > Input I only see "MacBook Pro Microphone":
System Information shows a FireWire iSight device, as well as an "Unknown Device". When I unplug the FireWire cable/dongle, both devices disappear.
This iSight is running the 1.0.2 firmware; I'll try to update it with 1.0.3 and test:
Why isn't the iSight mic working? How can I use an external iSight as an audio/video webcam in modern versions of macOS?
Related threads that seem to be experiencing the same issue: