All SpecTcl spectra have a gate applied to them. The apply command applies a different gate to a spectrum. One of the conditions for a gate to increment is that the gate applied to it must be satisfied (true) for the event that might increment it.
ungate replaces the gate applied to the
spec1 and so on with a predefined
gate named -TRUE-. As the name implies, the
-TRUE- gate is true for every event (it is
a gate of type T). This effectively removes
any applied gate from the spectrum.