At the receiving terminal _______ to separate the 8-digit se

At the receiving terminal _______ to separate the 8-digit sequences into the appropriate channels.
the codec is required
tha frame code is needed
PCM is used
a demultiplexer is arranged
Within the terrestrial system,the message signal is strong and ________ .
the noise power is very low
the niose power is also strong
the noise is very weak
the noise is in outer space
PCM is dependent on three separate operations,___________ .
coding,decoding and choosing
sampling,quantizing and performing
sampling,coding and decoding
sampling,quantizing and coding
For example,the signal ________ from a sattelite,located in far outer space,is very weak.
receiving
received
be received
in PCM system
词组“被传信号的波形”的英文是：
the shape to transmit signal
shape siganl to transmit
transmit signal shape
the shape of transmitted signal
“格式”的英文是：
form
format
formula
frame
“编译码器”的英文是：
codec
coder
decoder
unique
“参数”的英文是：
system
parameter
environment
attenuation
“同步”的英文是：
parameter
reexamination
environment
synchronization
“信噪比”的英文是：
known as the ratio
noise and signal
signal over noise
signal-to-noise ratio