Module A-117 is a combination module, including a digital noise generator and an 808 source.
The digital noise generator uses random sequences of square waves (18 step shift register with multiple feedback), whose rate can go from random clicks to pure noise. The colour of the noise is very different from the analog noise produced by the A-118. In addition to a manual setting, the rate can be controlled by an external clock - eg. VCO, LFO or MIDI clock. The 808 Source aims to re-create the sort of multi-oscillator array that was used in Roland's TR-808 and 606 drum machines as the basis of the sound of the hi-hat, cymbals and cowbell. The cowbell mix uses two oscillators, and the cymbals mix six.