| ISDN is a relatively old but not obsolete | | | | ordinary telephone copper wires, with an output |
| technology. It is often the base of more current | | | | of better voice quality. The medium of ISDN is |
| technologies. ISDN or the Integrated Services | | | | also used for video conferences where it provides |
| Digital Network provides fast connections and | | | | video, text and voice transmission to individual |
| clear quality of data transmission in digital phone | | | | desktop systems. |
| connections. ISDN allows sending of voice, video | | | | The connection best suited for residences and |
| and data over digital or analog phones | | | | small scale businesses is the ISDN BRI [Basic Rate |
| simultaneously. The transmission speed of ISDN is | | | | Interface]. In BRI, two B Channels and one D |
| 64kbps. ISDN is the international communication | | | | Channel is used. Hence, it is often referred to as |
| standard for data transmission. The various kinds | | | | 2B+D. The B Channels have data transfer rate of |
| of ISDN access interfaces are Basic Rate | | | | 64kbps, so combining them together, a BRI can |
| Interface [BRI], Primary Rate Interface [PRI] and | | | | provide up to 128 kbps of data. When subscribed |
| Broadband ISDN [B-ISDN]. | | | | to an ISDN BRI, the user gets two 64kbps digital |
| Two channels are used for communication in | | | | channels. These channels receive and transmit |
| ISDN. The first is the Bearer Channel or B | | | | video, voice and data simultaneously. An ISDN |
| Channel. The second is the Delta Channel or D | | | | Terminal Adapter is used to connect to the data |
| Channel. Data is transmitted through the B | | | | terminals and telephones in the users' premises. |
| Channel. Signaling and control are taken care of by | | | | ISDN technology is often the behind the scene |
| the D Channel. The D Channel can also transmit | | | | base of current digital data transmission |
| data. Here, it must be remembered that ISDN is | | | | technologies. Compared to analog system, ISDN |
| not a specific protocol. It is designed so as to | | | | allows clearer transmission of voice and faster |
| allow simultaneous access to data and voice. ISDN | | | | transmission of data. ISDN BRI is the most suited |
| is a circuit switched telephone network system. It | | | | connection for small businesses and residential use. |
| is able to digitally transmit voice and data over | | | | |