Lesson 3/Learning Event 6
c. Patch Panel, Model BP 353A.
This patching panel contains a
precision attenuator to insert 110 dB loss in 1 dB steps. The output of the
attenuator is connected through an impedance-matching transformer to the
external circuits.
The patching panel provides a 600 ohm load for the
voltmeter, enabling measurements in dBm as well as in corresponding volt
RMS.
Further, it provides facilities for matching impedances among
oscillator, voltmeter, and line. The patching panel is a passive unit; it
contains no amplifier. A frequency switch arranges the circuit to respond
to the oscillator in two ranges: 50 Hz to 5 kHz, and 5 kHz to 56 kHz.
Learning Event 6: NOISE-LEVEL-VU MEASURING SET, MODEL TTS-37B.
The TTS-37B shown in figure 5 is designed to measure noise and signal
levels, including speech.
It is a receptive device only; it does NOT
furnish a test signal.
a. Meter scale.
The meter has two scales.
The first scale (VU-DB)
reads level either in volume units (VU) or tone levels (dBm) of signals.
The second scale (dBrn) reads on very small signal levels because it
indicates noise. There is an offset of 10 dB between zero references of the
two meter scales.
b. Jacks. One monitor jack (MON DC) 6 provides a DC output which may
be used to drive a recorder. A second monitor jack (MON AC) 5 provides an
AC output which may be used to drive an impulse noise-measuring set, a
telephone headset, or an adjustable low-noise, high-gain amplifier.
c. Weighting. A switchable filter network provide C-message weighting
and two band weightings.
(1) C-message.
The C-message
weighting
filter
section
passes
frequencies between 0.7 and 2.5 kHz.
(2) High-pass. A filter section, called high-pass, is essentially a
bandpass filter that passes frequencies between 0.5 and 10 kHz.
(3) Low-pass.
Two low-pass filter sections give a choice of band
weighting from 0 to 3 kHz or 0 to 15 kHz respectively.
d. Dialing. Provisions are also made for dialing out, talking over the
circuit under test, and for holding the circuit.
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