A normal telephone hooked up to an ISDN modem's POTS port works just like a normal phone. Outbound calls also work exactly the same as if it were a normal, analog line. The cost of the ISDN varies from location to location. Typically, there is an installation fee, a monthly fee, and a usage fee. Contact your local phone company for pricing information.
Most ISDN users have both an analog line and ISDN line.
You need to have an ISDN modem powered up to talk over an ISDN line with your normal phone. If there is a power outage, you'll lose your phone service. As a safety consideration, it's best to keep both lines. Call your phone company and ask to be set up for an ISDN line. When ordering your ISDN line, be sure to specify that you want both voice and data over the same line if you want to be able to do voice communications on the ISDN line as well as connect with our system.