Table of Contents
Advertisement
Diagnostic Functions
Calibrate
The Calibrate test evaluates the voice output level of a CVSD voice channel. A 1 kHz tone is gen-
erated at each channel end, and transmitted to the remote channel; the system steps through the
adjustment range (-6 dB to +1.5 dB) until the voice output is at the switch-selected nominal output
level (0 dBm or +7 dBm). If the level cannot be attained, a Fail result is displayed. Otherwise a
Pass result is displayed, and you are given the option of saving or not saving the adjustment level
at which the voice channels pass the test. If you save the results, all configurations with a CVSD
voice channel at that channel number are changed, as well as the active configuration.
Gain Check
PCM and ADPCM voice channels use Gain Check to test the voice output level. A 1 kHz tone is
generated at each channel end, and transmitted to the remote channel; each channel output is sam-
pled to check if' the level is within +1 dB of the switch-selected nominal output level. The display
then reports Pass or Fail results for the channel.
VF Idle
The VF Idle Test evaluates the noise level in the system. The analog input of the voice channel
at the data origin node is grounded. The loopback may be local, with the loopback point at the
same node as the data origin, or may be remote, with the loopback point at the opposite node from
the data origin channel. The voice channel at the data origin voice channel module evaluates the
noise level in the loopback path, and develops an error count (in this test, errors are significant
deviations from ground in the returned VF signal). Figure 8-4 shows the loopback paths of a VF
Idle test with Node M as data origin point.
Digital Test
The Digital Test uses the digital circuitry of the data origin node voice channel to generate a dig-
ital "quiet channel pattern." If the data origin node is the same as the loopback point (a local loop-
back) the digital pattern is looped back at the interface between the Transmit/Receive Logic Plus
module and the channel module. If the loopback point specified is at the opposite node from the
data origin (a remote loopback) the digital pattern is looped back within the digital circuitry of
the remote channel module. The data origin module evaluates the returned digital signal, and de-
velops an error count which is displayed in the channel status scan.
This test is used after a VF Idle Test, to determine if a noise problem is originating in the digital
or VF section of the voice channel module. Figure 8-5 illustrates the loopback paths of a Digital
Test with data origin at Node M.
1 kHz Test
In this test, the voice channel module at the data origin node generates a 1 kHz tone; the tone is
digitized and sent through the selected loopback path. You must connect the test equipment to the
front panel VF Out test point, or the channel interface, to display or otherwise evaluate the re-
turned 1 kHz signal. If the loopback point is at the same node as the data origin (a local loopback),
the signal is looped back (as a digital signal) at the interface between the voice channel module
and the Transmit/Receive Logic Plus module. If the loopback point is at the opposite node from
Otherwise, a discrepancy exists between stored channel
parameters, and actual channel operation. If a different
configuration is activated, and the levels set in the new
configuration are the same as the stewed parameters for the
previously active configuration the voice levels set by the Rev dB
Levels routine remain, (the channel's voice output, level does not
change to the levels set in the newly activated configuration
8-13
036R660-000, Issue 10
Advertisement
Table of Contents
