Lesson 3/Learning Event 5
Figure 4.
Telephone Test Set AN/USM-181.
a. Oscillator, Model BP 204B. This Variable-Frequency Oscillator (VFO)
is capable of supplying a practically distortion-free sine-wave test signal
within the frequency limits of 5 to 560 kHz in five ranges.
The vernier
tuning gives a dial reading accuracy of 3 percent.
Output power is
adjustable to a maximum of 10 dBm into a 600-ohm load.
Output amplitude
remains practically constant throughout the entire frequency range. Power
is furnished by four internal rechargeable batteries, with recharge
capability from the 115/230-volt supply.
b. Voltmeter, Model HP 403B.
This voltmeter is capable of measuring
from 0.001 to 300 volts Root Mean Square (RMS), or signal levels from -72 to
+52 dB above 1 milliwatt (dBm) when terminated in 600 ohms over a frequency
range of 5 Hz to 2 megahertz (MHz).
Input impedance is 2 megohms, high
enough to allow bridging across circuits without loading.
The voltmeter
circuit is protected from excessively strong input signals by a 1/16-amper
instrument fuse.
Power is furnished by rechargeable batteries enclosed
within the case.
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