Examples of desired time controls:

initial time = 90 minutes
increment = 30 seconds/move
no time added during the game
(this is the official FIDE time control)

initial time = 100 minutes
increment = 30 second/move
add 50 minutes at move 40
add 15 minutes at move 60
(this is similar to 40/120, 20/60, SD/30) 

Most users of the FIDE Gametimer clock and the Saitek clock know how to set these time controls. 
But did you know that the Chronos can do it too?  The appropriate modes are Pr-C1A and Pr-C2A. 
These were not chess modes but intended for other games, but can be set to apply for chess as
well.  The modes allow you to set a time delay (zero) and an increment (30 seconds) for every
move.

To get these, press all three buttons down.  Then press the center button 37 times for Pr-C1A and
38 times for Pr-C2A.  Press the left button to select.  Press the center button for 2 seconds to
edit.

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First example (use Pr-C1A):  
Set the first display to [01 - 1:30] on both sides.  
Set the second display to [1:30:00] (no time delay).  
Set the third display to [0:30] (30 second increment).  
Set the fourth display to [0:00:00] (add zero extra time after move 1).  
Set the fifth display to [0:30] (30 second increment).  
Set the beep and LED on or off as you desire.  
Finally, save to one of your 12 presets.

The clock starts out reading [01 - 1:30] and [01 - 1:30].  After the first move by both players,
the clock may read [1:30:23] and [1:30:07] (one player used 7 seconds, the other used 23 seconds).
When one player runs out of time, that person's display becomes [0:00:00] and will never change
again (i.e. it won't add 30 seconds after you've run out of time).

-----------------------------------

Second example (use Pr-C1B):  
Set the first display to [40 - 1:40] on both sides.  
Set the second display to [1:40:00] (no time delay).  
Set the third display to [0:30] (30 second increment).  
Set the fourth display to [20 - 0:50] (add 50 minutes after move 40).  
Set the fifth display to [0:50:00] (no time delay).  
Set the sixth display to [0:30] (30 second increment).  
Set the seventh display to [0:15:00] (add 15 minutes after move 60).  
Set the eighth display to [0:30] (30 second increment).  
Set the beep and LED on or off as you desire.  
Finally, save to one of your 12 presets.

The clock starts out reading [40 - 1:40] and [40 - 1:40].  After the first move by both players,
the clock may read [1:40:23] and [01 - 1:40].  It only shows the seconds of the player whose move
it is until less than 10 minutes.  At move 40, the clock adds an extra 50 minutes to both sides. 
At move 60, it adds another 15 minutes.  Of course, after every move, 30 seconds are added.  When
one player runs out of time, that person's display becomes [0:00:00] and will never change again
(i.e. it won't add 30 seconds after you've run out of time).