Close, D-Gate is an input. (you might be thinking of the “gate out” which does pulse when Degree changes) When patched, Degree doesn’t do anything unless the D-Gate input is high. Effectively this is a sample+hold for the Degree control. It’s awesome for “sampling” a note from a sequence (mult your sequencer 1v/Oct out to Degree in and to your other voice(s), program certain gate/trigger steps to update D-Gate). It is also is used in the “Shift Register” mode on Telharm.
The H-lock (and associated trigger in) is a very cool feature - very under utilized, by myself as well.
With Flux turned up, you can select and “lock” certain harmonics, so that those harmonics will be heard regardless of where you turn Centroid. Imagine it’s like programming multiple bandpass filters that will then track pitch changes. Once you turn Flux all the way down, they’re released. I find it’s best to explore this feature just using the Telharmonic on it’s own at first.