nominal design fre- quency. As an example, the accuracy of an oscillator might improve from, say, +4.6 ppm to +16 ppb (now between 19,999,999.68 and 20,000,000.32 Hz). The frequency will still drift, but much less than a standalone oscillator running without the assistance of a more accurate source from elsewhere. Phase Synchronization As previously stated, phase synchronization can be described as the process of aligning the tick of the second hand on our clocks. In normal life, if all our clocks did not tick over the second at near the same instant, nobody would notice. However, many processes require a much more accurate alignment. To illustrate, imagine two industrial-type robots, neither of which has vision capability, passing ob- jects to each other in a factory assembly process. One of the robots is the sender (of the object) and one is the receiver. If you were to program the robot pair, then the steps, along with the time to start that step, might look something like the following. The timeline for the sender robot, with time in seconds, might be Step 1. Start + 0.000: Move robot arm to position X, y, Z Step 2. Start + 0.350: Check arm is in position X, y, Z Step 3. Start + 0.400: Open fingers to release object Step 4. Start + 0.600: Close fingers Step 5. Start + 0.650: Move robot arm to position 0, 0, 0 Step 6. Start + 0.850: Retrieve another object Step 7. Start + 1.000: Restart process The timeline for the receiver robot, with time in seconds, might be Step 1. Start + 0.000: Move robot arm to position X, y, Z - 100 (100 mm below the other robot) Step 2. Start + 0.350: Check arm is in position X, y, Z - 100 Step 3. Start + 0.400: Open fingers to catch object Step 4. Start + 0.600: Close fingers Step 5. Start + 0.650: Move robot arm to position 0, 0, 0 Step 6. Start + 0.850: Release object Step 7. Start + 1.000: Restart process For this coordination to work between the two robots, they must clearly agree when the time of 0.000 starts (regardless of the time of day); otherwise one robot will be dropping 