I, however, wish to address this issue of the pedal notes. Veery715 says that the pedal notes don't have a resonant point which locks them in. I beg to differ with that -- the real pedal notes start with the C an octave below the C often referred to on the trumpet as "low C" (written as middle C -- one ledger line below the staff). And they do have a resonance which locks them in. It is a physical property of closed acoustic systems like the trumpet that one can sound a wave whose wavelength is twice that of the enclosed vibrating air system. So pedal C is easy to lock in, as are the pedal B, Bb, A, Ab, G, F# (all seven valve combinations) below that.
The F, E, Eb, D, Db below the staff shouldn't be referred to as pedal notes because they do not exhibit the same physical tendencies as the "real" pedal notes. My trumpet teacher taught me that these notes are simply "artificial" notes since in order to play them we are taking "real" notes and forcing them down a 4th. The F can of course be played as a real note on most trumpets by using all three valves and extending the 1st and 3rd slides as far as possible, but for many people who try to play it with 1st valve, it's simply a low Bb which is played extremely flat in order to sound as an F.