From Arthur C. Clarke
's 2001: A Space Odyssey
The AE 35 unit was the control system for pointing the ship-Earth communication antenna on the space ship Discovery (I).
The AE 35 unit was located on the mounting of the ship-Earth radio dish, under a small hatch fixed with four wire-secured locking nuts. The unit itself was a small slab of solid state circuitry, about the same size as a post card. It was secured in its slot with two locking bars and had a small handle for easy removal. Two spare AE 35 units were on board Discovery I.
The ship's Heuristically programmed ALgorithmic 9000 series computer first detected an intermittent problem in the original AE 35 unit, predicting failure within 72 hours. Frank Poole removed the original unit and replaced it with a spare, but testing proved that the AE 35 unit was not faulty. HAL then claimed that the second AE 35 unit was going to fail within 24 hours. However, crewmen Poole and Dave Bowman postponed replacing the unit, as it was almost certain that the fault was in HAL's fault prediction circuits rather than either of the actual units. As a transmission from Earth was received on how to deactivate HAL the insane computer, the AE 35 unit did stop working, but this was found later to be caused by HAL himself. Frank Poole went on an EVA to replace the unit again, and was killed by when one of the EVA pods attacked him and ruptured his suit.
At this point, the game was up, and Bowman (now the only non-incapacitated crewmember on the Discovery) knew that HAL 9000 was insanely defective and that emergency action needed to be taken.