Hi

ISDN (Integrated Services Digital Network) is a type of digital phone/data and Internet service that preceded ADSL (Asynchronous Digital Subscriber Line) and has for the most part been superseded by it.

Normal telephone lines carry analog signals that must be amplified and converted to digital signals by the phone company. This process introduces not only a slight lag time, but also distortion in the signal. Dial-up modems and telephones are examples of equipment that use analog signals. ISDN makes use of digital signals running along existing copper lines to increase the data throughput, reduce line noise and enhance signal quality.

Thanks