Which statements are true regarding ISDN channels? (Select three)
A. Each B channel can transmit up to 64 kbps
B. The ISDN B channel carries voice or data
C. The ISDN D channel transmits control information.
D. The D channel transmission rate varies depending on the service used.
E. HDLC or PPP can be used to encapsulate D channel information.
Answer: A, B, C
Explanation:
Integrated Services Digital Network (ISDN) is essentially digital telephone service. ISDN envisions telephone companies providing “Integrated Services,” capable of handling voice, data, and video over the same circuits.
The two primary variants of ISDN are BRI (Basic Rate Interface) and PRI (Primary Rate Interface). BRI, sometimes referred to as 2B+D, provides two 64 kbps B channels and a 16 kbps D channel over a single 192 kbps circuit (the remaining bandwidth is used for framing). The D channel is used for control information. BRI is the ISDN equivalent of a single phone line, though it can handle two calls simultaneously over its two B channels. PRI, essentially ISDN over T1, is referred to as 23B+D and provides 23 B channels and a 64 kbps D channel. PRI is intended for use by an Internet Service Provider, for example, multiplexing almost two dozen calls over a single pair of wires.