The iriput signal is fed via SKI to the first active stage built around ICl. Configured as a noninverting amplifier whose gain is set by the ratio of R3 and Rl. In this case, the gain is set at unity. This initial stage is required to isolate the following stage from any loading effects. The output from ICl is fed via three frequency shaping networks to IC2
The three networks built around RV1, RV2, and RV3 are also included in the feedback path of IC2, another inverting op amp stage. The components associated with the three variable resistors are chosen to give the required frequency control.