ISDN stands for Integrated Services Digital Network, and is a digital phone system connection which allows data to be transmitted simultaneously across the world using end-to-end connectivity. ISDN connections are installed the same way normal phone lines are except your local telephone carrier must install and prepare the phone line for digital service and a ISDN adapter must be installed in your computer or on your network. Once in place, ISDN provides the customer with a digital local loop. Typical analog local loops require the carrier to utilize Pulse Code Modulation (PCM) to encode the analog signals for digital transmission (analog-to-digital conversion) which can introduce latency and noise. By keeping the signal digital the entire time, ISDN avoids the problems associated with analog modem connections. ISDN connections have data transfer rate ranging from 64Kbs to 128Kbs often referred to as 1B channels or 2B channels. ISDN is well suited for the small to medium office or heavy Internet user.
ISDN offers many advantages over analog connections, including:
Higher speed
Faster call setup
Less expensive than leased lines
Ability to run voice and data simultaneously
ISDN remains a viable remote access solution despite other emerging WAN technologies (DSL, cable) for these reasons:
ISDN can be offer in places that DSL or cable are not.
Many companies (including service providers) have invested heavily in ISDN equipment and training.
Remote offices can use ISDN to connect directly to central offices without traversing the public Internet; most DSL and cable implementations require connecting with the central site via VPN over the Internet.
