Tape Deck Synchronization
Don't expect the DA7 to help you sync multiple recorders: it can only slave to timecode. You'll have to take care of recorder sync yourself.
Modular Digital Multitracks
MDMs like the ADAT and DA-88 family already have this issue covered, and usually all they need is the appropriate sync cable between decks. One deck is designated the master, all the rest are slaves. Using external (BRC for ADAT, MMC-38 or -88 for Tascam) or internal (SY-88) devices, you can have the master deck spit out SMPTE Longitudinal Time Code (LTC) or MIDI Timecode (MTC) to feed to the DA7. (Many of these devices also allow you to slave the decks to external timecode too.) Users slaving to video may generate timecode farther upstream, but the result is still a timecode stream for the DA7.
Synchronizing analog decks to each other (and to timecode) usually requires some kind of synchronizer box connected to all the decks to keep their motors locked.
The DA7 SMPTE Card
The DA7's optional SMPTE sync card plugs into a special fourth slot dedicated to that card. You feed it either composite video or SMPTE LTC and the DA7 slaves to the incoming signal. If you have MTC in the studio, you generally won't have or need this card.
The DA7 won't send out SMPTE, nor will it help you stripe a tape with timecode.
The DA7 echoes MIDI Time Code (MTC) to the "toPC" port which is nice. But it doesn't appear to echo MTC to the MIDI Out port — at least, I haven't been able to get it to do so.