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Apollo Command Module Signal Conditioner Equipment (SCE), measuring approximately 20″ x 10″ x 6″, with several markings on the sides: "45700-501-111, 06359-0414BJA," "45717-501-1," and "SE280A-40328-106-131, 06359-0410BJA." The top panel is marked "C13-1A106," with ten ports marked "J1" through "J10."
Manufactured by North American Rockwell's (NAR) Autonetics Division, the hermetically sealed electronics package resided in the Apollo Command Module's lower equipment bay and drew 28 volts DC/35 watts. The SCE transformed signals from sensors and transducers to basic 0 to 5 volt DC instrumentation analog (coded measurements) voltage level. Signals were then distributed to the Pulse Code Modulated (PCM) telemetry and Command Module displays and provided excitation voltages to some of the instrumentation sensors and transducers.
The SCE contains a DC differential amplifier assembly, DC differential bridge amplifier, AC to DC converter, DC active attenuator, and redundant 20, 10, and 5 volt DC power supplies. Also included is an error detection circuit which automatically switched to the redundant power supply if the primary power supply voltages fell out of tolerance. A switch on the spacecraft's main console also permitted manual toggling between power supplies—it was this switch that was flipped by astronaut Alan Bean during the launch of Apollo 12, preventing an abort and restoring telemetry after a lightning strike disabled the spacecraft's electronics.
