Cases were aluminum box extrusions discovered at a local surplus dealer (unfortunately sold out!) Grooves molded into sides holds PC board without additional hardware.
Left to right: 4-pin male XLR for standard headset, 1/8" (3.5mm) mini-jacks for cheap computer headsets, call/mute switch and signal indicator, and volume control.
XLR female and male 3-pin connectors for loop-through (daisy-chain) interconnection of intercom units with standard mic cable. On the right is an external signal light output jack (for TV camera use).