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Abgieich der Laufzelt und der Farbtragerphase
Da bei einem zentraltaktgesteuerten Videosystem alle
Gerate unterschiedlichen
Standort und somit unter-
schiedliche Leitungslangen besitzen, muB jede dieser
Signaiquellen an der gemeinsamen Mischeinrichtung
hinsichtlich Laufzeit und Farbtragerphase exakt iiber-
einstimmen, um Farbtonfehler und Horizontallaufzeit-
fehler zu vermeiden.
Abgleich:
@ Gerit auf ,Sync. Extern" stellen mit Taste @).
@ Auf einem Zweikanaloszilloskop die Horizontallauf-
zeit mit Einsteller @8) so einstellen, da8 die negativen
Flanken
der S-Signale beider Signaiquellen
zur
Deckung kommen.
@
Einen Kanal invertieren und beide Signale addieren.
@ Mit dem Phasen-Grobsteller @) und Feinsteller @4)
das Burst-Signal auf ein absolutes Minimum oder
zum Verschwinden bringen.
Bei eingerasteter PAL-Phase leuchtet die griine LED @
auf.
8.2.1 Anwendung der ,,Schrift-
einblendung"
Alignment of the transition time and the chroma carrier
phase
Since all devices are at different locations and thus have
different cable length in a video system controlled by a
central clock, each of these signal sources must exactly
agree in terms of transition time and chroma carrier
phase so as to prevent color-tone faults and faults of
horizontal transition time.
Alignment:
@
Set the unit to "External Synchronization" with the
button @8).
@ Adjust the horizontal transition time on a two-
channel oscilloscope with the adjuster @6) in such a
manner that the negative slopes of theS
signals from
the two signal sources coincide.
@
Invert one channel and add the two signals.
@ Using the coarse phase adjuster @) and the fine ad-
juster @4) cause the burst signal to decrease to an
absolute minimum or to disappear altogether.
The green LED @) lights with enganged PAL phase.
8.2 "Text Superimposition" option
Characters can be superimposed in the combination
test pattern instead of the 250 kHz square-wave signal.
A circuit board is available as option equipment for this
purpose; it is retrofitted in the factory and can be pro-
grammed according to the wishes of the customers.
The customer may choose from among 16 different text
lines with a four-bit switch. Each text line consists of up
to 15 characters (including spaces).
Since the E-PROM is programmed in a customer-speci-
fic manner, the character complet is unlimited, i.e.,
lower-case letters, upper-case letters, numbers, sym-
bols, and the like can be superimposed.
Since the E-PROM is socket-connected, it may be re-
placed, thereby offering the possibility of subsequent
modification. The text lines can also be switched se-
quentically at a one-second rate.
8.2.1 Application of the "Text Super-
imposition"
Text superimposition permits the VG 1000 to be also
used in cases where job-specific data must be dis-
played in addition to the test pattern. For example, trans-
mitter identification data are superimposed by broad-
casting institutions, video channels can be identified in
video facilities, and cable channels can be identified.
Videotapes can also be unambiguously identified (for
example as mother tape or Copy 1).
Continous texts with automatic sequencing can also be
displayed for advertising purposes.
The slow- and quick-motion
functions
of video
re-
corders can be checked in a simple manner with the au-
tomatic text sequencing.
For this, a white field of the size of a character is pro-
grammed in each text line in such a manner that the
white field appears at the 1st position inthe 1stline, atthe
2nd position in the 2nd line, and so forth, until it appears
at the 15th position in the 15th line. With automatic se-
quencing, there is a withe field moving on the screen
from left to right, so that the slow-motion, quick-motion,
fast forward, and fast rewind functions can be checked.
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