For Telephone voice Transmission to use a T line, the signal must be __________________ before the multiplexed.

For Telephone voice Transmission to use a T line, the signal must be

1.	For Telephone voice Transmission to use a T line, the signal must be __________________ before the multiplexed.
A.	Synchronized
B.	Modulated
C.	Sampled
D.	Filterd
Answer» D. Filterd