The Behringer Abacus Dual function generator in detail:

Abacus by Behringer is a 1:1 clone of the popular dual-function generator Maths by Make Noise. The module is one of the most versatile modulation sources on the market and covers a wealth of functions: Envelope, LFO, Slew Limiter, Attenuator, Envelope Follower, Logic and Mixer. It generates various control voltages and processes supplied CVs. Modulation cycles between 25 minutes and 1000 Hertz with sometimes unusual waveforms are no problem for this module. The main focus for most users should be on envelope and LFO functionality. With the Rise, Fall and Curve controls and the Cycle button you can adjust the most important parameters quickly. The curve shape of the Rise and Fall parameters can be adjusted continuously from exponential to linear to logarithmic. On top of that, Rise and Fall each have their own control voltage inputs and can also be modulated together via Both. Four inputs with their own attenuators, two of which each pass through a function generator page, are output via outputs 1-4 matching and additionally combined at the main outputs OR, SUM and INV.