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AM5(e) Classic Instruction Manual
6.4.2 Test Setup for Notch Noise: For a typical notch noise measurement, there must
be a hold-tone signal on the measured circuit. For end-to-end tests using AM5(e)
Classic units, the far-end unit SEND function should be set to 1004 Hz at a level
sufficient to ensure a received level of greater than -40 dBm, while the near-end
MEASURE function is set to NOISE W/T. (Refer to Figures 5-3, 5-4, and 5-5 for
typical locations of equipment).
Where a responder is installed at the far-end, an external handset should be
connected to the DIAL terminals, the DIAL function selected, and the
responder's number called. When the responder answers, send the appropriate
code to put it into the "send 1004 Hz" mode.
For loopback tests, one AM5(e) Classic is used. The SEND selection is 1004 Hz
and the MEASURE selection is NOISE W/T.
6.4.3 Noise Weighting Filters:
Noise measurements (CMSG for the AM5; PSHO for the AM5e Classic). Other
filters may be selected by the left FILTER key to "weight" the measurement over
the band of frequencies that is important for the circuit. Filters are described in
detail in Sections 7 and 8. A summary of filter types will also be found in sub-
section 3.3.17.
6.5
MEASURE NOISE TO GROUND (NTG)
Noise-to-Ground is measured by internally summing the signals on the Tip and Ring
wires on the measured circuit within the AM5(e) Classic, then measuring the noise
through a selected filter, with reference to ground.
The ground reference must be connected through the ground screw terminal on the
rear panel (Figure 3-4) or through the sleeve contact of the RX (or TX/2W if in a 2-Wire
LINE selection) bantam jack.
6.5.1 Noise to Ground Measurement Range: The range of the noise to ground
measurements differs from those shown in sub-section 6.3 in that the range is
shifted toward the high-level end as follows:
•
AM5 Classic
•
AM5e Classic
The NTG level is displayed in the left display window, while the right display
window is not used. If the NTG level is below those shown above, "undr" is
displayed. (Refer to example under 6.4.1). The following shows a 100 dBrn
measurement (on an AM5 Classic). The AM5e Classic would read 10 dBm (not
shown) for the same noise level.
SEND
MEAS
DISPLAY
November 19, 1997
(18-0047)
The default filter selection is usually used for Notch-
40 to 129 dBrn at ±1.5 dBm
–50 to +39 dBm at ±1.5 dBm
dB
dBm
dBrn
mSEC
HOLD TONE
Page 6-5
MEASURE FUNCTIONS
NTG
KHz
SEC
MIN
CNT
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