c. Loading and Data Transmission. Loading consists of inserting values of
inductance in the line to reduce attenuation. However, you know from studies
of electrical fundamentals that inductance tends to oppose changes in current.
Although adding L to reduce amplitude-frequency distortion is a practical
solution to one problem, the L in the loading coils causes another problem if
high-speed data are to be sent over the line. The higher frequencies which are
part of the data signal will be greatly affected, causing so much envelope-
delay distortion as to possibly make the received data signal nearly useless.
As a general rule, telephone circuits will perform better in data communication
if they are not loaded.
STUDY EXERCISES
In each of the following exercises, select the ONE answer that BEST
completes the statement or answers the question.
Indicate your solution by
circling the letter opposite the correct answer in the subcourse booklet.
1. A transmitter circuit in a telephone has two power sources: voice power
and battery power.
In the circuit of figure 3, Appendix A, the transmitter
controls the output power by
a. applying the ac voice signal directly to the line.
b. varying the resistance in series with the battery.
c. varying the direct current in the secondary circuit.
d. rectifying the voice current to provide dc in the primary circuit.
2. When a standard level of voice signal power is dissipated in a 600-ohm
precision resistor, the standard voltage of 0.775 is developed.
These
conditions produce the standard voice power, which is
a. 1 milliwatt.
c. 0.01 microwatt.
b. 0.1 picowatt.
d. 0.001 milliwatt.
3. Circuit conditioners must know the effects of attenuation on a telephone
line. Attenuation on a telephone line causes
a. noise level to rise.
b. voice power to be reduced.
c. induced voltages to appear.
d. crosstalk to interfere with communication.
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