Integrated Services Digital Network (ISDN)
ISDN is a set of communication standards for simultaneous digital transmission of voice, video, data, and other network services over the traditional public switched telephone networks.

Asymmetric Digital Subscriber Line (ADSL/DSL)
Enables faster data transmission over copper telephone lines rather than a conventional voice band modem can provide.
Bandwidth is greater to the customer premises (downstream) than the reverse (upstream). This is why it is called asymmetric.