ISDN (Integrated Services Digital Network)

A widely available high bandwidth switched network service providing end-to-end digital connectivity over standard phone lines for simultaneous transmission of voice and data. There are two levels of service:

1.  Basic Rate Interface-ISDN (BRI-ISDN)–provides for digital transmission of two 64 kbps bearer channels and one 16 kbps data and signaling channel (2B+D).

2.  Primary Rate Interface-ISDN (PRI-ISDN)–provides for digital transmission of twenty three (23) 64 kbps bearer channels and one (1) 64 kbps data and signaling channel (23 B+D).