this is only a speculation so not take it for granted:
[DCA] - Since the V-FUG is actually an oscillator with CV input for the frequency, the DCA should be some kind of Control Amplifier that controls the range of the incoming signal and therefore the oscillator frequency.
[T-DSC] - In the manual abreviasions all units starting with T are units that receive a Trigger signal and all units ending with SC are Scaler units(T-VSC & T-BSC). Since its output is connected to T-ENV, which is an envelope generator, I think it should provide some kind of Trigger. This trigger is controlled by the FUG. an oscillator, probably operating as an LFO, the source for steady rhythmic triggers?