Integrated Services Digital Network (ISDN) is a set of communication standards for simultaneous digital transmission of voice, video, data, and other network services over the traditional circuits of the public switched telephone network. It was first defined in 1988 in the CCITT red book. Prior to ISDN, the telephone system was viewed as a way to transport voice, with some special services available for data. The key feature of ISDN is that it integrates speech and data on the same lines, adding features that were not available in the classic telephone system. The ISDN standards define several kinds of access interfaces, such as Basic Rate Interface (BRI), Primary Rate Interface (PRI), Narrowband ISDN (N-ISDN), and Broadband ISDN (B-ISDN). 

ISDN is a circuit-switched telephone network system, which also provides access to packet switched networks, designed to allow digital transmission of voice and data over ordinary telephone copper wires, resulting in potentially better voice quality than an analog phone can provide. It offers circuit-switched connections (for either voice or data), and packet-switched connections (for data), in increments of 64 kilobit/s. In some countries, ISDN found major market application for Internet access, in which ISDN typically provides a maximum of 128 kbit/s bandwidth in both upstream and downstream directions. Channel bonding can achieve a greater data rate; typically the ISDN B-channels of three or four BRIs (six to eight 64 kbit/s channels) are bonded.

1. When was ISDN first defined?
2. Where?
3. What does it stand for?
4. Does it support video?
5. What else?
6. What is its key feature?
7. was this available before?
8. What does BRI stand for?
9. What kind of interface is BRI?
10. Can you name other kinds?
11. What are the name of two others?
12. What kind of switches does ISDN use?
13. Can you utilize any others?
14. Which one?
15. What does that do?
16. What kind of wire is used?
17. Does this lead to better or worse quality?
18. How many kilobits are utilized?
19. Whats the max bandwidth?
20. Is that for both directions?
21. What can result in a higher rate?
22. How many are bonded?

Numbered answers:
1. 1988
2. in the CCITT red book
3. Integrated Services Digital Network
4. yes
5. speech
6. it integrates speech and data on the same lines
7. no
8. Basic Rate Interface
9. access interface
10. Yes
11. Narrowband ISDN (N-ISDN), and Broadband ISDN (B-ISDN)
12. circuit-switches
13. Yes
14. packet-switched
15. carries data
16. copper
17. Better
18. 64 kilobit/s
19. 128 kbit/s
20. yes
21. Channel bonding
22. three or four