Modular synthesis has enjoyed something of resurgence, with artists such as DeadMau5, Junkie XL, and Scanner all employing it in their music. Modules connect to the bus board via ribbon cables, and many modules require 12 volt direct current to operate. Connecting modules to the bus board is a simple case of connecting the two via a ribbon cable supplied with the module. Modular synthesis consists of two signal types: audio and control voltages. Audio signals are similar to control voltages; the only difference is the polarity and the voltage. Modular synthesis starts with a sound source: the oscillator. Voltage-Controlled Amplifier in modular also acts as a gate. There are many modules available for the Eurorack system, covering everything from wavetables through to sequencers, creative modulation options, granular synthesizers, logic modules, and samplers, through to spring reverbs, delay units, and microphone input modules.