Cisco Model D-PCG1000 PowerKEY CAS Gateway Referencia técnica
August 2006
Operations Alert Bulletin
Muting Issues with the GQAM
and GoQAM Modulators
Background
The Cisco® GQAM and GoQAM modulators have four RF output ports that support
16 QAM-channel frequencies. Occasionally, a site may have data or telephony
devices (like cable modems) configured to use one of these frequencies. Under such
a scenario, system operators can mute the specific GQAM or GoQAM frequency in
order to eliminate interference between the modulator and the data or telephony
device.
Cisco engineers have recently discovered that if a soft reset is performed upon a
Cisco engineers have recently discovered that if a soft reset is performed upon a
GQAM or GoQAM modulator with a muted frequency, the muted frequency
becomes un-muted until the modulator reboots. This action introduces interference
with the data or telephony device.
Note: Soft resets are performed from the DNCS GUI, a craft port command (using a
Note: Soft resets are performed from the DNCS GUI, a craft port command (using a
laptop), or from the front panel of the GQAM or GoQAM modulator.
Recommendation
Cisco recommends that system operators configure their sites so that data and
telephony devices do not share frequencies with any of the QAM-family of
modulators.
For sites that chose to configure data or telephony devices to use one of the 16 QAM-
For sites that chose to configure data or telephony devices to use one of the 16 QAM-
channel frequencies, Cisco offers the following recommendation concerning resets of
a GQAM or GoQAM modulator: reset your GQAM or GoQAM modulator with a
hard reset, rather than a soft reset. The GQAM or GoQAM modulator will not un-
mute previously muted frequencies during the hard reset.
Note: A hard reset is accomplished by either unplugging (and then re-plugging) the
Note: A hard reset is accomplished by either unplugging (and then re-plugging) the
GQAM or GoQAM modulator or by toggling the on/off switch.