Module A-140 is an envelope generator, and, since it puts out control voltages, counts as one of the modulation devices in a modular system.

As soon as the gate input receives sufficient voltage, the ADSR generates a variable voltage, changing in time, called an envelope. This varying voltage is output in normal (positive) and inverted form, and can be used, for example, for voltage controlled modulation of a VCO, VCF, or VCA, or for processing other modules' inputs and outputs. The shape of the envelope is governed by four parameters: Attack, Decay, Sustain and Release. The envelope is started (triggered) by a gate signal either from the INT.GATE voltage on the system bus, or, if a signal is put into it, from the gate input socket. The envelope can also be re-triggered, ie. start from scratch again, each time a trigger signal is sensed at the Retrig. input socket, when the gate is still open. Module A-140 includes a three-position toggle switch to select one of three time ranges. The envelope duration ranges from about 50us (microseconds) up to several minutes.

In combination with the Comparator module A-167 a free-running "ADSR-LFO" can be realized.