There were a few sync devices around back in the day. I used a Fostex 4050 with an Alesis HR16 drum machine and possibly an MMT8 sequencer (though I didn't use the sequencer for long before moving to computer). I also had a JL Cooper PPS100 but it wasn't as reliable at reading code as the Fostex. I seem to remember Tascam made similar devices too.
If you don't mind using proprietary time code there were a few cheaper devices around too. I'd suggest digging around the Muzines website for reviews in magazines like Home and Studio Recording or Sound On Sound.
Fostex’s SMPTE reading/writing, MIDI syncing, auto-locating, remote transport control unit recently underwent a serious internal re-examination. Ed Jones assesses the newly implemented features and describes their practical application.
It depends on the gear you have? What can the sequencer read and write? MIDI, SMPTE, proprietary? Then what your 4 track can support - You will probably end up with a piece of hardware sitting between the two JL Cooper units were popular back when this quaint way off working was common.
@jamesperrett I had read those articles, thanks for confirming that I was on the right track.
@rob aylestone The 4 track is the master, the sequencer reads MIDI sync. Currently they can sync by going 4 track → MOTU Midi Express → DAW → sequencer, the DAW simply reads SMPTE and sends out MIDI sync, just acting as a SMPTE to MIDI sync converter. I was wondering if that conversion was available in a hardware box, and according to the answers here it appears that it is.