Trackrat has explained it well. I will add to this.
You would need to "stripe" SMPTE time code to the analog tape on one track (preferably tracks 4 or 5, as tracks 1 and 8 are on the other sides of the tape, and are more prone to being damaged from storage and rubbing against the reel. Time code NEEDS to be preserved well for it to work well. This is a great rule to follow for more important tracks that carry a lot of high frequency information on analog tape. Bass guitar and kick drum are two very good candidates for tracks 1 and 8.).
You will need the BRC for this too work. The BRC will generate SMPTE time code, AND read it. You would do it like this:
1 - Run a cable from the BRC's SMPTE output to the tape decks input. If you are recording at +4 or -10 on the analog deck, you need to make sure that the BRC is outputting this same operating level, which is selectable on the BRC (refer to manual for how to select this.)
2 - Put a tape in the ADAT machine. You need to run tape in the ADAT for the BRC to output SMPTE, because the SMPTE is derived from the proprietary time code on ADAT tape.
3 - Start the ADAT Play, and the analog decks play and record the SMPTE. There are SMPTE offset's available on the BRC and those should be applied (the BRC manual has a good explaination of SMPTE offsets too!).
4 - Hook up a cable from the analog machines output to the SMPTE input on the BRC, and select External Sync for the BRC. Press play on the BRC (the ADAT tape will not move yet because there is no incoming time code for it to follow), then press play on the analog deck. The ADAT will now start to play, and will take a bit of time to "sync" with the incoming time code.
Some warnings!!!
ADAT's like to see VERY stable time code!!! Since the SMPTE is being generated from your analog machine, if the reel motors on your machine are not rock solid, the ADAT MAY not stay in sync with the incoming time code from the tape. This is all about timing issues. The ADAT NEEDS to have stable timing to follow, and if the tape machines motor is fluctuating too much, the ADAT will not be able to stay in sync!
You will need to have plenty of "leader" for the ADAT to sync with the incoming time code. This can be as little as 5 seconds, and as much as 20 seconds. Probably around 8-10 seconds will be what works. What this means is that you will want to have at least 8 seconds of tape roll before you engage Record on the ADAT so that it can get in sync with the incoming time code. The ADAT WILL NOT record until a sync is achieved. Your milage may vary in regards to how long sync takes.
When you stipe the analog tape, it is a good idea to set the ADAT to -5 seconds to start. You would then start the analog machine first, then start the ADAT. The SMPTE code then will start at 22:59:55:00 (23 hours, 59 minutes, 55 seconds, 0 frames) , and when the ADAT get's to 00:00:00:00, you will have that on the analog tape. You will want to go ahead and stripe the whole analog tape in one pass.
When you go to record on the ADAT, you will want to start the recording at around 00:00:10:00 (10 seconds). This way, you will have that first 10 seconds of ADAT tape to run before it start recording.
I will be honest, I have tried to make older analog machines sync with ADAT, and did not have great luck. Some analog machines just don' t have motors that are stable enough to make this happen. If yours is, GREAT!!! If not, you will either need to have the motor serviced or replaced, or abandon the idea. Before you go buying all the stuff you need to make this happen, you may want to borrow a BRC and try it out to see if it will work with your analog deck.
Good luck!
Ed