External iSight microphone audio not working

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. In 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: - https://apple.stackexchange.com/questions/412824/how-to-update-external-isight-firmware/412825 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: - https://discussions.apple.com/thread/250914849 - https://discussions.apple.com/thread/251255964 - https://discussions.apple.com/thread/251293054 - https://discussions.apple.com/thread/252233406