How do I synchronize the outputs of multiple Model 3390 Arbitrary Waveform Generators?

How do I synchronize the outputs of multiple Model 3390 Arbitrary Waveform Generators?

1. Connect the 10MHz output on one unit to the 10MHz input on the other unit(s).
2. Set all instruments to the same frequency.
3. Set the phase relationship between the instruments by pressing UTILITY and selecting OUTPUT SET UP.
4. Then select Adj Phase.
5. Adjust the phase until you get the required phase between the units.
6. Use an oscilloscope to verify the phase relationship