15
2-45. In an afts transmit system, the conversion
of dc signals into audio tone-shift signals
is done by which of the following pieces
of equipment?
1. Cryptographic
2. Tone terminal set
3. Converter/comparator
4. Modulator/demodulator
2-46. The process of simultaneous
transmission of several intelligible
signals on the same frequency during the
same period of time is called
1. duplexing
2. simplexing
3. complexing
4. multiplexing
2-47. What are the two methods of
multiplexing?
1. Time-division and frequency-
multiplication
2. Time-division and frequency-division
3. Time-multiplication and frequency-
multiplication
4. Time-multiplication and frequency-
division
2-48. In time-division multiplexing, assume
that a 4,000-hertz tone is applied to each
of six channels in a telegraph transmitter
and that each channel is to be sampled at
a rate of 2. 5 times during each cycle of
the 4,000-hertz tone. At what speed, in
revolutions per second, must the rotating
switch turn to accomplish this sampling
rate?
1. 3,000
2. 4,000
3. 7,200
4.
10,000
2-49. In time-division multiplexing, what
drawback is encountered if an excessive
number of frequency channels is used?
1. Static is increased
2. Bandwidth is increased
3. Switching becomes unreliable
4. Reception becomes unintelligible
2-50. How many times per cycle is a practical
time-division multiplex system
optimumly sampled?
1.
1.5
2.
2.0
3.
2.4
4.
3.1
2-51. Frequency-division multiplexing systems
transmit and receive during a maximum
of how many degrees of a sinewave?
1. 90
2.
180
3.
270
4.
360
2-52. By using frequency-division
multiplexing, tty circuits may carry a
maximum of how many single, 3,000-
hertz channels?
1.
12
2.
16
3.
18
4.
24
2-53. In a 16-channel tty-multiplexing system,
the maximum difference between a mark
and a space, for any give channel, is how
many hertz?
1. 85
2.
382.5
3.
425
4.
467.5
