Toshiba TW40F80 manual Section Vi Dual Circuit, Outline, Principles Of Operation

SECTION VI: DUAL CIRCUIT

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

• 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.

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.

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.)

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