Question

what are t carriers? a the signaling channels in an isdn line b dedicated digital telephone lines used in europe c the data channels in an isdn line d dedicated digital telephone lines used in north america

Explanation:

T - carriers are dedicated digital telephone lines, and they are used in North America. Option A is incorrect as signaling channels in ISDN are different (like D - channels). Option B is wrong because dedicated digital lines used in Europe are E - carriers. Option C is incorrect as data channels in ISDN (like B - channels) are not T - carriers.

Answer:

D. Dedicated digital telephone lines used in North America