Vassil...
In general, what Nat says is correct, I will add to it. I bought my first PRS before ShopBot produced a drill for it, and I did a great amount of experimenting in this area. I have used many different options for both plunging and switching, wont say I'm an expert, but have drilled tens of thousands of holes testing electric, hand held inline (like the SB) and the ARO industrial programmable drills. I have recorded video of most different actions. Here is one of the ARO drills working as you desribe: http://www.youtube.com/user/Islaww1#p/u/5/Tr5TvVV5YNE
Although this worked, it requires the drill to traverse its entire stroke for each hole. This is usually 3-4 inches. The plunge speed can be adjusted somewhat with flow controls, but it usually takes a good number of tests to get good results. In order to insure that the machine "stays" in position till the hole is completely drilled, I added prox switches to the bottom of the stroke. When slow plunge speeds are required, it is not efficient to plunge 3-4" to drill 1/4" deep holes. This is the only option for drill control that I am aware of that will work with Gcode. Other than those drills that run continuously during a drill cycle, this configuration uses the most air. Air is used to plunge, retract and drill for each hole.
In 2009 ShopBot software developers added some "trickery" to the code that triggers an output during a plunge only move. This allowed users of the SB drill to add the dual control as Nat refers to above and cut air consumtion considerably. It also decreased cycle times. Here is a video that was taken just after this new code was implemented. It shows the drill plunged for the complete drilling file, and the enhanced code turning on the drill, only during the down drill move. http://www.youtube.com/user/Islaww1#p/u/7/QmYlwc4Cmlw
This advancement has shown to use the least air, and allow full software control of the plunge speed. This may be the best feature of the PRS style drill over the PRT. I have used plunge speeds ranging from .125 to over 4 inches per second. This range of adjustment is not avalable using flow controls on plunge cylinders. This is one of those areas where we SB users have an advantage over Gcode machines.
Hope this clarifies those drill actions.