Toshiba TW40F80 - Manual (Page 44)

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1. OUTLINE
DUAL circuit performs the signal process, etc. on the sub
screen and is composed of the followings as shown in Fig. 6-
1.
• Video/color/deflection (V/C/D) process
• On-screen display (OSD) superimposing process
• Sub-screen process, memory
• Main/Sub screen picture superimposing process
• Sub screen control microprocessor
2. PRINCIPLES OF OPERATION
DUAL circuit is composed of the following functions.
(1) Double window sub screen 1/2 compression process
(2) Sub screen still process
(3) 9-screen multi-search process
(4) Main/Sub screen superimposing process by YIQ sig-
nal.
• 9-screen multi-search process
The sub screen process IC (TC9092AF) is the IC using the
programmable technology and can realize various functions
such as sub screen 1/2 compression, 9-screen multi-search,
etc. by switching the program.
The 9-screen multi-search process is carried out by selecting
the channel on the right half of the wide screen with 16:9
aspect ratio and the picture images received are projected on
the 9 screens from the upper left screen in order.
The search is carried out by approx. every 2 seconds repeat-
edly. When the next picture image is searched, the picture
image on the previous screen becomes a still picture. When
the 9 screens are finished projecting (to the picture image on
the right bottom screen), the search operation is carried out
repeatedly from the upper left screen.)
SECTION VI: DUAL CIRCUIT