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AM5(e) Classic Instruction Manual
6.3.2 Test Setup for Idle Line Noise: For a typical noise measurement, there must be
no signal on the received line. For end-to-end tests using AM5(e) Classic units,
the far-end unit SEND function should be set to QUIET while the near-end unit
MEASURE function is set to NOISE. (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 QUIET mode.
For loopback tests, one AM5(e) Classic is used. The SEND selection is QUIET
and the MEASURE selection is NOISE.
6.3.3 Noise Weighting Filters:
line noise measurements (CMSG for the AM5 Classic; 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. Noise
Weighting Filters for the AM5 Classic and AM5e Classic are described in detail
in Sections 7 and 8, respectively. A summary of filters will also be found in sub-
section 3.3.17.
6.4
MEASURE NOTCH NOISE (NOISE W/T)
The Noise with Tone test (also referred to as Notch Noise test) measures noise on a
circuit which has a 1004 Hz tone applied to it. (On many types of circuits a signal is
required to hold the circuit active.) The tone is removed in the measuring circuit of the
AM5(e) Classic through a 1010 Hz notch filter, then the residual noise is measured.
Both level and frequency displays operate when this function is selected. (See 6.3 for
units of noise measurement).
6.4.1 Validity of Notch Noise: In order for a Notch Noise measurement to be valid,
the AM5(e) Classic must be receiving a tone as indicated by HOLD TONE being
lighted (green). When HOLD TONE is lighted it indicates that the received
signal is at a frequency of 995 Hz to 1025 Hz at a level greater than –40 dBm.
(individual units may vary slightly in this range). If there is measurable noise,
the noise will be displayed in the left display and the frequency of the hold tone
will show in the right display.
The UNDR (under-range) indication will be displayed, if the noise is below the
measurement range, and the frequency will not be shown:
SEND
MEAS
DISPLAY
November 19, 1997
(18-0047)
The default filter selection is usually used for idle-
dB
dBm
dBrn
mSEC
HOLD TONE
Page 6-4
MEASURE FUNCTIONS
NOISE
W/T
KHz
SEC
MIN
CNT
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