Cisco Continuum DVP Models D6238 & D6239 8VSB Demodulators (NTSC) Data Sheet
Model 6275 Frequency Agile Demodulator
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Operation
The Model 6275 Demodulator receives off-air or cable signals, processes them, and provides a complete set of interface
features for the demodulated outputs. These include two buffered baseband video signals and demodulated audio.
Additionally, the Model 6275 Demodulator provides balanced stereo audio, selectable mono or SAP outputs, and a front panel
headphone jack for monitoring the audio output.
features for the demodulated outputs. These include two buffered baseband video signals and demodulated audio.
Additionally, the Model 6275 Demodulator provides balanced stereo audio, selectable mono or SAP outputs, and a front panel
headphone jack for monitoring the audio output.
Applications
In Demod/Remod headend applications, off-air signals are integrated with CATV signals. This is accomplished by using the
separate video and audio outputs from the Model 6275 Demodulator as inputs to conventional modulators.
The audio output from the Model 6275 Demodulator is directly compatible with either the 4.5 MHz subcarrier input or
baseband audio inputs of most common CATV modulators. The subcarrier interface is preferred to maintain optimum BTSC
stereo audio performance. For mono audio applications, the baseband audio is available from the left and right XLR connector
on the Model 6275 Demodulator rear panel. This connector interfaces to the baseband audio input on the modulator.
Additional applications of the Model 6275 Demodulator include:
· Baseband signal delivery out of digital trunking
separate video and audio outputs from the Model 6275 Demodulator as inputs to conventional modulators.
The audio output from the Model 6275 Demodulator is directly compatible with either the 4.5 MHz subcarrier input or
baseband audio inputs of most common CATV modulators. The subcarrier interface is preferred to maintain optimum BTSC
stereo audio performance. For mono audio applications, the baseband audio is available from the left and right XLR connector
on the Model 6275 Demodulator rear panel. This connector interfaces to the baseband audio input on the modulator.
Additional applications of the Model 6275 Demodulator include:
· Baseband signal delivery out of digital trunking
· Backup for existing fixed channel demodulators
· Headend performance monitoring for FCC Proof of Performance measurements
· Headend interconnections—source and hub headend interface capability
· Headend signal loss monitoring via Status Monitoring and Control (SNMP)
Technical Details
Tuner and IF Functions
The Model 6275 Demodulator provides frequency agile tuning for broadcast and cable applications. In broadcast mode, the
Model 6275 Demodulator covers channels 2 through 69. In cable mode, the demodulator tunes to EIA channels 2 through 125.
As an additional input, an external IF can be applied for demodulation. This feature allows demodulation of signals when used
in digital IF transport applications.
Model 6275 Demodulator covers channels 2 through 69. In cable mode, the demodulator tunes to EIA channels 2 through 125.
As an additional input, an external IF can be applied for demodulation. This feature allows demodulation of signals when used
in digital IF transport applications.
Video Functions
Synchronous video detection is a standard feature of the demodulator. This capability provides precise demodulation of the
Vestigial Sideband Signal (VSB) transmission format, and allows video signal quality to be accurately measured. The
television signal depth of modulation is measured using the zero carrier reference pulse. This pulse momentarily switches off
the picture carrier to simulate 100% modulation. Both this level and the sync tip level provide the scaling necessary to
measure depth of modulation.
Another feature is the automatic frequency compensation. In case the received signal has an in-band frequency slope (due to
long cables or other external causes), the unit can equalize the signal and make sure that the frequency response after
demodulation will be flat.
Vestigial Sideband Signal (VSB) transmission format, and allows video signal quality to be accurately measured. The
television signal depth of modulation is measured using the zero carrier reference pulse. This pulse momentarily switches off
the picture carrier to simulate 100% modulation. Both this level and the sync tip level provide the scaling necessary to
measure depth of modulation.
Another feature is the automatic frequency compensation. In case the received signal has an in-band frequency slope (due to
long cables or other external causes), the unit can equalize the signal and make sure that the frequency response after
demodulation will be flat.
Audio Functions
All possible audio outputs are simultaneously available at the rear. These modes are:
· Stereo, where stereo outputs on L and R are provided on the rear panel.
· Stereo, where stereo outputs on L and R are provided on the rear panel.
· Mono, where both the L and R rear panel connectors carry mono (L+R) audio regardless of whether stereo is present.
· SAP, where a separate connector provides the signal when it is available.
· SAP/Mono, where SAP is on a separate connector and Mono is available on both L and R connectors.
Audio Outputs
Four types of audio signal outputs are available at the rear panel. They include:
· 4.5 MHz subcarrier
· 4.5 MHz subcarrier
· Composite, wideband BTSC format
· Baseband, discrete L, R, or mono audio
· SAP, discrete mono audio
Remote Operation
As one of the first demodulators on the market to have this feature, the Model 6275 Demodulator can be controlled remotely
via SNMP over Ethernet. This allows the operator to integrate this unit into any kind of management system using the SNMP
interface capabilities. The unit also fits entirely in the ROSA/TNCS system.
via SNMP over Ethernet. This allows the operator to integrate this unit into any kind of management system using the SNMP
interface capabilities. The unit also fits entirely in the ROSA/TNCS system.