Computer Networks - Computer Networks Section 2
51. What signal-to-noise ratio is needed to put a T1 carrier on a T0-kHz line ?
- Option : D
- Explanation : To send a T1 signal we need
Hlog2, (1 + S / N ) = 1.544 x 106 with 50,000.
S / N = 230 -1,48 ~ 93 db.
- Option : B
- Explanation : In the case of go-back-n protocol, when a NAK is received, all the frames sent since the last frame acknowledged are retransmitted. Go ----> Back ----> n.
- Option : C
- Explanation : In bipolar code, the signal varies among three levels. In non-return to zero code, the signal remains the same through-out the bit cell. In unipolar code, there will be no signal either below zero or above zero. In Manchester code, the signal level will not vary in the middle and is unipolar.
