Arturia KeyStep Pro Keyboard with Advanced Sequencer and Arpeggiator - Manual (Page 65)

4.3.3. Clock Section
These three jacks (In, Out, Reset Out) allow you to interface with modular synthesizers
and pre-MIDI technology that was capable of clock synchronization (such as early drum
machines produced by Korg and Roland).
The KeyStep Pro is capable of both sending and receiving synchronization signals. It also
has a Reset Out, allowing external sequencers with a reset input to re-start from the
beginning of a sequence whenever a KeyStep Pro sequence is restarted.
Please see Chapter 7 [p.132] for information about clocking and synchronization.
Arturia - User Manual Keystep Pro - KeyStep Pro Overview 59