It's been years, not much I remember about operation. Some units were/are set up with a single-pin plug in the panel (maybe as big in diameter as a headset plug, IIRC), the drill was, you downloaded the database to a laptop, then used a cord to plug into the panel, with avionics powered up. I think it took about 10 minutes in the plane. The cord was, of course, some proprietary thing, you needed a serial adapter of some sort. The database cartridge, I think, about the size of a cassette tape, was in the back of the unit, you had to pull the whole thing out of the panel to get to it. (Front loading cards came with the KLN94, or the above mentioned KLN900). I don't even know if it was possible to update databases to the cartridge "at home," I never saw anyone with an adapter like Garmin uses. Usesr may have had a subscription that actually mailed the cartridge, kind of like netflix DVDs.