Editing Apollo Guidance Computer (section)

===Timing===
The AGC timing reference came from a 2.048&nbsp;MHz [[crystal oscillator|crystal]] [[clock rate|clock]]. The clock was divided by two to produce a [[clock signal#4-phase clock|four-phase 1.024&nbsp;MHz clock]] which the AGC used to perform internal operations. The 1.024&nbsp;MHz clock was also divided by two to produce a 512&nbsp;kHz signal called the ''master frequency''; this signal was used to synchronize external Apollo spacecraft systems.

The master frequency was further divided through a ''[[clock divider|scaler]]'', first by five using a ring counter to produce a 102.4&nbsp;kHz signal. This was then divided by two through 17 successive stages called F1 (51.2&nbsp;kHz) through F17 (0.78125&nbsp;Hz). The F10 stage (100&nbsp;Hz) was fed back into the AGC to increment the [[real-time clock]] and other involuntary counters using Pinc (discussed below). The F17 stage was used to intermittently run the AGC when it was operating in the ''standby'' mode.