The Sony Wireless Timecode License Key works with Sony's CBM smartphone app to offer two methods of syncing timecode among multiple PXW-Z90 and HXR-NX80 cameras.
Either set one camera's timecode as the master and sync the other cameras to it, or manually set the timecode to time-of-day or as you prefer on one camera and then sync the others. This license requires the use of the CBM (Content Browser Mobile) smartphone app, which is compatible with iOS 9.0 through 10.3 or Android 4.4 through 7.1.