The keyboard encoder in the Heath H-19 terminals (also the Zenith Z-19) was a National Semiconductor part. It was discontinued in late 1981 or 82, while the terminal was still in production. Heath bought tens of thousands of them in a "last time buy" both for ongoing production and for future service. I don't know the current availability of this item from Heath (Heath does still exist, and does sell SOME parts), but it hasn't been available from National for a decade and a half. It WAS a generic part at the time. Note that every H/Z - 89/90 has an imbedded H/Z-19 terminal and therefore uses this part. I'm not sure of this, but I think that the ROM was required because the encoder only generated a "key number" and not ASCII, and it wasn't easily possible to arrange the keys for the key number to correspond to the ASCII value (Carl Goy was the designer, and he's still around out in California somewhere, he worked for Mouse Systems and Headland Technology after leaving Heath). I know all of this because for 5 years I was the Product Line Director for the entire Heath/Zenith computer line. Barry Watzman