[IBM ISDN board with TI DSP, COM1 interface, 64kbps]
The big problem with ISDN is still getting connectivity to the people you want to talk to and getting service at reasonable prices (prices vary widely depending on your phone monopoly's interactions with the regulatory bureaucracy, and/or your distance from long-distance service providers if you want PRI connections.) Do you know if the TI DSP is user-programmable, or if it's just performing most of the ISDN functions? The difficulty with COM1 interfaces, when you're using DOS, is that DOS basically gives you a single character per interrupt, which means a system doing 8000 char/second on COM1 is taking a *lot* of interrupts. There are generally other interfaces that let you handle more characters at once, but they're not transparent to software that's expecting simple COM1, and they're often vendor-specific. (The FOSSIL drivers for 16550 UARTs are addressing the same problem; maybe somebody's got FOSSIL support for ISDN?) On the other hand, if you're doing software to support voice over ISDN, it's probably worth doing some board-specific hacking, especially if you're going to use the on-board DSP anyway. Bill