Editing Apollo Guidance Computer (section)

===Standby mode===
The AGC had a power-saving mode controlled by a ''standby allowed'' switch. This mode turned off the AGC power, except for the 2.048&nbsp;MHz clock and the scaler. The F17 signal from the scaler turned the AGC power and the AGC back on at 1.28 second intervals. In this mode, the AGC performed essential functions, checked the standby allowed switch, and, if still enabled, turned off the power and went back to sleep until the next F17 signal.

In the standby mode, the AGC slept most of the time; therefore it was not awake to perform the Pinc instruction needed to update the AGC's real time clock at 10&nbsp;ms intervals. To compensate, one of the functions performed by the AGC each time it awoke in the standby mode was to update the real time clock by 1.28 seconds.

The standby mode was designed to reduce power by 5 to 10&nbsp;W (from 70&nbsp;W) during midcourse flight when the AGC was not needed. However, in practice, the AGC was left on during all phases of the mission and this feature was never used.