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2) Types of picture signal modulation.
The CCITT recommendations specify the methods of picture signal modulation for the different facsimile classifications
as listed below.
CCITT & Recom-
mendations
Modulation
Method
Actual waveform
Eas
£é=nPee ee
t
!
1
WHITE
BLACK
WHITE
Phase modulation
2400 bps
4800 bps
4 bits for white, 4 bits for black and 4 bits for black are encoded as 10110111011.
G3
(V27 ter)
e Example of phase modulation (2400 bps)
10s
be)
Oe
0)
AC/DC amplitude
modulation
7200 bps
9600 bps
e AC/DC amplitude modulation is a type of phase modulation.
[Fig. 15]
3) Types of control protocol signal modulation.
Tonal signal and binary signals are used to control protocol signals. Tonal signals are used for analog facsimiles, and
binary signals are used for digital facsimiles.
* Tonal signal
Tonal signals are single-tone signals having different frequencies.
Note the three different total signal frequencies as follows.
1100 Hz
2100 Hz
+ Binary procedure signals.
Binary procedure signals use numeric value 1 and 0, which are separately converted into two different frequencies
(1,650 Hz for 1 and 1,850 Hz for 0).
A total of 300 numeric values are transmitted per second.
Binary data is expressed using numeric value 1 and 0, and bits are the units of binary data.
Consequently, the 300 numeric values are 300 bits of data.
The bps (bit per second) is used to indicate the data transmission rate per second.
In this way, the binary procedure signal is transmitted at 300 bps.
Data
0
1
1
1
1
Waveform
'
1
f
'
'
'
1850Hz
1650Hz ' 1650Hz ' 1650Hz | 1650Hz | 1650Hz ! 1650Hz ' 1850Hz
[Fig. 16]
1
t
'
1
1
4) Transmitted Data Spectrum
37
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