软件水平考试网络工程师英语复习练习题 10 套第 1 套ISDN,which stands for Integrated Services Digital Network, is a system of digital phone connections, which has been available for over a decade
This system allows data to be transmitted simultaneously across the world using (1) digital connectivity
With ISDN,voice and data are carried by bearer channels occupying a bandwith of (2) (bits per second)
Some switches limit B channels to capacity of 56 Kbps
A data channel (3) handles signaling at 16Kbps or 64Kbps,depending on (4)
Note that,in ISDN terminology,”k” means (5),and not 1024(2^10) as in many computer applications
therefore,a 64Kbps channel carries data at a rate of 64000bps
A new set of standard prefixes has recently been created to handle this
Under this scheme,”K”(Kilo) means 1000(10^3),”M” (Mega) mean