I have one of these adapters, and they're very simple things. They don't have the smarts to "add extra scanlines" or do any format conversion of any kind. They just take the raw signals for the internal CRT, and do simple buffering and a couple of inversions. That's it. IIRC, the resulting signals are of the right polarities to interface to a TTL monitor, but the sweep rates are sufficiently off so that many TTL monitors will fail to sync.