18.
Assume that a circuit conditioner arrives to connect a telephone modem
having 600-ohm input impedance.
If his test of output impedance of
the line shows it to have 135 ohms impedance, what action should he
take?
a.
Insert a matching transformer between line and modem.
b.
No action
is
necessary
because
line
impedance
is
within
tolerance.
c.
Raise the transmitting level to overcome line loss so normal
level enters the modem.
d.
to be in error.
SITUATION
Assume that you are performing the longitudinal balance tests of input
and output circuits as shown in figures 1-14 and 1-15.
Exercises 19 through 23 are based on this situation.
19.
One step in the procedure to measure longitudinal balance in either
the input or output circuit is to measure the
a.
voltage
between
the
electrical
center
of
the
wire
pair
and
ground.
b.
voltage between each of the two wires to ground.
c.
input and output impedance of the wire pair.
d.
resistance of each wire to ground.
20.
Assume that the input circuit is being tested. If the normal signal
level (0 dBm0) at the point of test is 0.636 volt, the value of V1
must be adjusted to
a.
1 milliwatt in 600 ohms.
b.
equal the normal signal level.
c.
0.636 volt from either line to ground.
d.
0.775 volt from transformer center tap to ground.
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