A synchronization method developed by Roland around 1980. A DIN sync cable carries two signals, a gate signal that tells the slave device to start or stop, and another signal that sends short timing pulses. Under the Roland standard, the pulses are sent at the rate of 24 pulses per quarter note (same as the MIDI clock message rate), although some Korg drum machines use 48 pulses per quarter note.
Unfortunately the DIN sync standard calls for a cable that uses the same connector as a standard MIDI cable, which often leads to confusion. The pinout is different and a MIDI cable will usually not work as a DIN sync cable, or vice versa. Fortunately, at least the standards are arranged so that connecting a MIDI output to a DIN sync input, or vice versa, will not cause any damage; it just won't work.