Sound powered phones. Usually located in a box in the space you were in. You plugged them into a special socket and could talk to others on the same circuit or they could patch circuits together in Engineering Central.
30 posted on 05/18/2014 7:33:28 PM PDT by cva66snipe
((Two Choices left for U.S. One Nation Under GOD or One Nation Under Judgment? Which one say ye?))