PC connection is "X-sync" and no TTL is available. Olympus did make TTL off-camera cords but they are rare now. I agree with a previous comment about moving up to the OM 4: the flash socket on the OM4 is integral to the pentaprism. On the OM1n, OM2n, it is a separate fiddly, vulnerable and fragile (read: prone to cracking) thing that was the Achilles Heel of the OM1, Om2 series. Cracking was so common in the time when I used the OM1n (later moving to the OM4) that I ordered several flash shoes (at the 1980s price of $25 each) just to keep up, as flash was used a lot for simple portraiture.
Originally Posted by BetterSense
If you need to keep the detachable flash shoe operational (when cracking up), it calls for drastic first aid: use SuperGlue in the crack, followed by an all-around Araldite/epoxy 'paint'. Don't get any of the stuff around the knurling ring or underneath where the contact pin is; just enough to cover the crack inside and out. It will probably give a while of service after this.