Message Circuit Noise Measurements; Sf Skip - HP 4935A Operating And Service Manual

Model 4W5A
To obtain loss deviations relative to 1004 Hz, the I,E:VEI,%ERO button is pressed during reception
of the 100.4 I fz reference signal. The received power level is stored (in dHm) and simultaneously displayed as
The IO04 flz reference level will not have to be subtrartrd from levels at other frequencies to obtain dR
readings.
According to telephone industry convention, attenuation is defined as a change in loss of a
telephone circuit, compared to the loss of a nominal 1000 Hz signal on that circuit. For example, a circuit
with 6 (it% more loss at 2800 Hz would have an attenuation distortion of +6 dH.
3-30.

SF SKIP

frequency signaling units. Any skipped frequency can be programmed using the STORE capability of the
3-32.

MESSAGE CIRCUIT NOISE MEASUREMENTS

The message circuit noise measurements determine the effects of background noise and tones.
( Q U I E T T E R M I N A T I O N )
TRMT TIMS
termination on one end (supplied by the transmitting 49XA) and a weighted measuring device on the other
end (receiving 4935A).
The C-message filter measures noise signals that annoy the typical telephone service subscriber.
valid for data transmission since the response characteristic is relatively flat over most of the frequency
range for data transmission (600 to 3000 Hz, see Figure :S-6).
The 3 kHz flat filter has a response that provides much less attenuation to the low frequencies (60
Hz to 500 Hz) than the C-message filter. By comparing a 3 kHz flat noise measurement to a C-message noise
measurement, the relative influence of low frequency noise (60 Hz commercial power, 20 Hz ringing, etc.)
can he determined (see Figure Z-7).
TELEPHONECIRCUIT
T
I
Figure 3-5. Message Circuit Noise Measurements
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M O N I T O R
RCV
Operation