How to choose an ISDN device

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If you plan to connect more than one machine, use an ISDN router.
If you need 128K throughput, use an ISDN router, or if you must go the cheap route, an internal card.
If you need POTS functionality, use an external TA or router, and choose carefully- POTS quality varies widely between vendors.
If you're paying per channel-minute and need to add/drop the second B channel based on bandwidth used, go with an ISDN router.
If you want to use the two B channels in two different locations or dedicate them to two different purposes, you need an external NT-1 and S-interface devices.

Some Hints

If you plan to only use PPP and perhaps analog ports, the "best" solution is the most expensive one- an external ISDN router instead of a "modem", connected to one (or many) computer with an ethernet card. An ISDN router provides the throughput of an internal card, but with lower CPU load, the ability to use POTS jacks without booting your PC, and for upgrades you just load new flash code (firmware). Plus it makes it very easy to connect multiple machines without having to dedicate one as a router. The downside is that while a TA may run $280-$400, a router runs $800-$1200.
Reviews of selected ISDN Routers and TAs

Kevin Kadow / kadow@msg.net