HD, think of busy single runway airports where the departure order could be fed into Time Based Separation software.
Presently, departure gaps are about 6 Miles, sometimes less in a strong wing and sometimes more after heavy arrivals. What if the TBS indicators were tailor made for each departure? You could have 90 seconds for a 737, 110 for a heavy, you could even have the aircraft weight included in the equation so each departure gap was individually calculated for each departure.
All the radar director would see was an indicator precisely calculated for the next departure and all the air controller needs to know is the next gap is custom made for their next departure.
you could increase the hourly movement rate at busy, single runway airfields by 10-20%.
And no electronic gizmos to distract anyone.