Pro Tools provides the following for configuring MIDI Machine Control (Master) settings.When the Enable option is selected, Pro Tools is the Master and it sends MMC commands to the slave device and receives MTC information back from the slave device.The MIDI Out Port pop-up menu lets you select the MIDI Out port to which the slave device is connected.The MMC ID setting lets you specify the MMC ID number for which MMC information will be sent. MMC commands contain an ID number to identify which machine should respond to the MMC command. There are 128 MMC ID numbers, from 0–127. The default of ID #127 is a special setting that transmits to all 128 MMC IDs. With a setting of 127, Pro Tools will transmit MMC commands to all MMC IDs.The Preroll setting lets you specify a pre-roll time in frames for your MMC slave device. Pre-roll is needed to provide the device with sufficient time to lock to the timecode transmitted by Pro Tools. This value will vary depending on the external device. If the pre-roll time is insufficient, the device may not be ready to lock until after the current timecode position has passed.