Wegener Communications UNITY 4600 ユーザーズマニュアル

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800032-01 Rev. G

27

This chapter provides an overview of 

 operation, details of controls and 

indicators, the alarm/warning system, and user interface details.

From one selected RF input feed, the 

 receives an L-band RF carrier from 

an external antenna LNB. It then demodulates the carrier and extracts the transmitted 
MPEG transport stream. If the stream is scrambled and the unit is properly authorized, 
it applies the descrambling algorithm to re-generate that transport stream as it 
appeared at the multiplexer in the uplink compression system. (Alternately, if using 
per-program viewing access, only the authorized programs will be descrambled.) This 
transport stream is then supplied to the ASI transport output, perhaps with program re-
mapping or conditional DPI filtering (under network control). The 

 also 

decompresses the components of a selected program and provides the audio, video, 
and/or data services for output.

Note:  The user or network may wish to have a null program assignment if no 

attempt at local decompression is desired. This is required for the new HD 
programming.

As needed, auxiliary functions are also provided, such as re-insertion of vertical 
blanking interval data (closed captioning for example) in the video output. 3.1 presents 
a logical block diagram of 

 operation.

Available outputs from the 

 include:

 

DVB-ASI transport output with program (number and descriptor) mapping

 

Decompressed MPEG video as composite video output (NTSC or PAL)

 

Two independent, decompressed audio streams (MPEG or Dolby AC-3 downmix) to 

balanced analog audio outputs

 

Re-insertion of VBI line data from various proprietary and ATSC protocols

 

Alarm relay

 

User control relays for cueing

 

DTMF cueing tones

 

Front-panel audio (one stereo pair) and composite video monitor outputs

If unable to deliver required services to predetermined standards, or if unable to detect 

a required network control stream (COMPEL

®

), the 

 attempts to resume 

normal operation through a process called Automated Recovery. Referring to an 
internal, non-volatile list of "presets", the 

 will attempt to restore either 

services or network control, depending on what caused the recovery. A "preset" is a 
list of unit settings, and the list of these presets is called the Preset Table. Automated 
Recovery will attempt to restore the unit according to each preset (one at a time) in the 
order in which they are listed in the table. The process continues (repeating attempts if 
necessary) until the unit successfully resumes normal operation or is halted by local 
user command. If successful with a preset, the settings in that preset become the 
permanent unit settings. Later, the local user (or the network, if available) may abort the 
results of the Automated Recovery and force the unit back to its last commanded setting.