Apollo Spacecraft S Band Communication System, Part 25—Central Timing Equipment

As the project to reassemble an Apollo Command Module’s communication and electronics system from original equipment continues, the next peak to be scaled is the Central Timing Equipment: the box which generates and distributes all of the timing signals to the on-board electronics, from the time stamps for telemetry, the mission elapsed time clock on the control panel, to the signal sent to spacesuits to purge waste water. This box presents a particular challenge, since it is welded shut, and an industrial computed tomography scanner must come to the rescue to figure out what is going on inside.

Timing was mission-critical in Apollo—most of the functions of the unit were triply redundant, with a voting circuit to provide uninterrupted, correct signals in case of failure of internal components.

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