This site maintains a vast database of old modem drivers. Registration may be required, but the site is legitimate for vintage hardware.

Cause: IRQ conflict or incorrect COM port assignment. Fix: In Device Manager → Properties → Resources → Change settings. Uncheck "Use automatic settings" and manually select an unused IRQ (e.g., IRQ 5 or 7).

Search GitHub for Firstcom or ISDN drivers. Several vintage computing enthusiasts have archived these drivers in public repos.

Critical Note: No official driver exists for Windows 10 or 11 64-bit for the FC 136. You will need to use a compatibility layer (explained below).

The Firstcom FC 136 is a legacy ISDN terminal adapter (often functioning as an external modem/router) popular in the late 1990s and early 2000s. It was widely used for ISDN (Integrated Services Digital Network) connections, providing faster dial-up and data transfer rates than traditional analog modems.

If you have stumbled upon this device in an old office, a warehouse, or a retro-tech project, you face one major challenge: modern operating systems no longer natively support this hardware. Finding a safe, functional source to download software Firstcom FC 136 has become a niche but critical task.

This guide provides you with everything you need—from driver sources to step-by-step installation on Windows 10 and 11.