The Synthrotek ADSR is a narrow envelope generator for the Eurorack system that generates either AR or ADSR envelopes. A switch can be used to select between exponential and linear characteristics. The envelope generator has two CV inputs, where the "ADSR" input modulates attack, decay and release (in ADSR mode), whereas "REL" only changes the release time. The applied control voltage is added to the ADSR control voltage and the release time is increased.