Many networking systems are designed to send a packet once every 125 microseconds. This is rather unfortunate because advanced coding algorithms are now capable of digitizing speech at significantly less than 64K bits per second. There are two primary technologies for providing fast data transmission over telephone lines. This system sends a digital signal from your home to the telephone central office. An ISDN telephone has a codec built into it to convert the analog signal to digital.
Computers can transmit data over an ISDN phone line using an ISDN interface.
A modem is not required since there is no analog to digital conversion. The B channels can be used for voice telephone or for computer data. The three channels are combined over the ISDN phone line using Time Division Multiplexing. Some industry observes believe that ISDN has lost its opportunity to be successful in the market place. The technology has been available for decades, but the phone companies generally asked a rather high premium for this service.