Nope, The serge NTO don`t have thru-zero FM, it have linear and exponential FM and a VCA for voltage control of index.
I wish my NTOs had it....
Josue.
Here's why I had deja vu, check out the Dynamic Depth Linear Frequency
Modulation description on the NTO page of the old Serge catalog:
http://www.carbon111.com/serge1982.pdf
And, like I said, it certainly acts like this, right down to the
dedicated VCA....