Vintage ZX1800A Ver 4.0 internal fax/data modem on an 8-bit ISA card, circa 1992–93. Built on the Sierra Semiconductor SC11075CV chipset with socketed firmware ROM, Takamisawa RY5W-K relay, onboard speaker, and dual RJ11 jacks (line/phone). FCC ID H4TZX1848A.

The 8-bit edge connector means this card works in everything from original IBM PC/XT-class machines through 386/486 AT systems — a genuinely useful era of compatibility for retro DOS builds, BBS setups, and vintage telecommunications projects. COM port selection (COM1–COM4) via jumpers, with the settings conveniently silkscreened right on the board.

Note: the empty IC socket (SC22101 position) is a factory configuration option, not a missing component — the board was manufactured this way.

UNTESTED — pulled from an estate lot of vintage PC components and sold as-is for parts/repair per vintage hardware standards.

Cosmetically clean with bright gold edge contacts, no corrosion or damage visible, QC stamp intact on solder side. Comes in an anti-static bag.

Ships fast, well-protected