A pre-MIDI synchronization scheme used most notably on Roland drum machines (including the TR-606, TR-808, TR-909, TB-303, and MC-202) and synths. Sync 24 was also called “DIN” Sync because it employed a 5-pin DIN connector, the same one later adopted for MIDI. Pin one transmitted 0-volt “stop” and 5-volt “Start/continue” messages, while pin three transmitted 5-volt timing pulses at a rate of 24 PPQN. Pin two was the ground. NOTE: although the sockets are the same, NEVER attempt to connect MIDI gear to Sync 24 gear. Bad things will happen.
A few other manufacturers adopted Sync 24 but it was superseded by the development of MIDI.