< Are there any ISDN adapters are available for a NuBus Mac that will support these modems? >
None of the 'true' ISDN adapters work with the BiSurfr or 3Com. In fact the BitSurfr" doesn't even work with the BitSurfr Pro. Those devices are a real mess.
ISDN falls into 2 flavors
1) the original (true) ISDN adapters for PCI and NuBus. Foresight, Leonardo, and Planet. They support the traditional protocols" HDLC, X.25, x.75 and so on. They all work with each other. They support up to 128K.
2) the asynchronous ISDN adapters - these were designed for low - cost internet access mainly. BitSurfr, 3Com Access, and the GeoPort adapter. These devices support V.120 and (some) PPP. Some of these work with each other, but its best to stick with the same brand and model. These support up to 56K.
Group #1 is for high speed file transfers and Host usage. Group #2 is for end users connecting to their ISP. Most commercial BBS will want to have modem, true ISDN and asynch ISDN so that any customer can connect, and TeleFinder supports this.
