The 700 serie is Synton’s first modular synth.

The 300 serie was the second generation modules.  They were 5 HE high

It used a matrix-board (not shown) to interconnect the modules. The I/O are at the back connector of the PCB

Some standard 700 modules and 1 custom modules

Some 700 modulesSVF 317

Custom build 700 system with matrix