Apple Workgroup Server 8550 - Manual (Page 75)

About your server’s sound ports
The sound input port is marked with an icon of a microphone. The sound
output port is marked with an icon of a speaker.
The server’s sound ports accept these 3.5 mm connectors:
The smaller connector (a “stereo miniplug”) is found most often on stereo
equipment. The slightly longer connector is found on the Apple PlainTalk
Microphone and other voice quality microphones. If your equipment has a
different type of connector, you can purchase an adapter at an electronics
supply store.
Extended miniplug Stereo miniplug
Sound input port
Sound output port
66 Chapter 3 / Expanding Your Server and Connecting Other Equipment