This is quite a rare analog modular synth and as a result, little is known about this classic analog. RSF is a French synthesizer company named after Ruben & Serge Fernandez. The Modular Model 11 is a towering modular system very similar to the common ARP 2600. Its basic specs are 3 oscillators in an analog monophonic synth which makes for some great bass, growls and blippy sounds. There's at least 1 LFO, VCF and VCA section with the classic sets of features for editing. A remote 61 note keyboard controls the Modular 11 via CV/Gate--no Midi here. There is a cool phaser effect for thickening your sounds for nice lead synths or wobbly sounds. It also has generous overdriven sounds and punchy ADSR and filter sections. It has 3 audio inputs which can be used to run external sounds through its filters and other modules. Pretty cool, but too rare to ever find.