posted 08-06-2006 10:19 PM               

The mainframes generally only provided numbers, usually in columns, on the console screens. The work the computers did was to extract the parameters from the telemetry stream, verify they were correct (not garbled that is), and then translate them in the values (units) used by the flight controllers. Sometimes the translation included comparing the value to a norm or limit.

The numbers were then displayed on a CRT screen, and a full-sized "background" slide which had descriptive text and titles was positioned over the CRT. A TV camera then looked down on this composite image and every console viewing that "display" simply saw that TV camera image on their screen.

Consoles could "control" which display and matching background slide were called up by dialing in a specific display number. This caused the display system to tell the mainframe which CRT/slide overlay set to use (i.e., which "channel"), and further caused the proper background slide to move in front of that CRT. The selecting console's monitor was then attached automatically to that channel.

Other consoles could then simply go to that "channel" to watch the same display (or jump back and forth between different displays).

There was no local "hardcopy" capability (no printers). Instead, for this and other reasons, each console was equipped with a "P-tube" similar to that used to day in drive-in banking. This P-tube system extended throughout the control center for moving paper from console to console. When a flight controller hit his "hard copy" button on particular TV channel, the composite image was printed on thermal copy paper at a central location which include a print-out of the requesting console. Technicians stationed at these hard copy machines would take each hard copy and place it in a P-Tube and send it to the requester.