I've always wanted one of these.
The 1045 is virtually a whole synthesizer in one package.
It has a VCO, a low pass VCF, a VCA & two envelope generators.
EG 1 controls the VCF, and EG 2 does the VCA.
The module seems to be made up of half a 1023 VCO, a 1006 filtamp (except that there is no audio mixer at the input) and two 1003 envelope generator circuits.
I really like the sound of the filter in this module. It gives great character.
The outputs of both envelope gens can also be used to modulate other modules.
The EG outputs are here too.
The VCF & VCA can either be voltage controlled externally with other modules or internally with old fashioned knob tweaking and/or the built in EGs. How versatile !!
An envelope is initiated when signals are applied to both the gate (shown by the square) & trigger (the decaying pulse) inputs. This is what happens from the keyboard.
The output of the EG stays at the sustain level for the duration of the gate.
Without a trigger signal, the EG will still output a voltage so long as there is a gate.