isr.co.ro : glossary Analog port A connection point on some ISDN (Integrated Services Digital Network) terminal adapters, that is, on the ISDN equivalent of a modem, where you can plug in ordinary non-digital telephones (or POTS, for plain old telephone systems), answering machines, and even standard modems. Most ISDN lines can act as regular telephone lines as well as digital data connections, but you can't plug normal telephone devices into an ISDN line without this feature or an equivalent stand-alone analog adapter.