JPH0149230B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a television receiver equipped with a video input terminal to which an external video signal is applied and a plurality of input terminals to which character/graphic information from the outside is applied. In particular, it relates to mode switching means.

Conventional configuration and its problems When switching modes in a conventional television receiver that has both a video input terminal and an RGB input terminal (8-pin input terminal, 21-pin input terminal), for example, if the video input is If there are inputs, video 1, video 2, and video 3, respectively, TV mode → Video 1 → Video 2 → Video 3 → RGB
→The TV mode and screen could be switched.

At this time, when you have switched the screen to Video 1, if you want to see the image of the television signal coming from the antenna (referred to as a TV image), you will need to switch the mode four times: Video 2, Video 3, RGB, and TV. However, it is time consuming and practically inconvenient.

Therefore, if we add a function that always returns to TV mode when switching channels on the television receiver using the channel switching pulse that occurs when switching channels, it would be possible to use the channel switching pulse that occurs when switching channels. mode), when you want to watch a TV image, you can immediately get the TV image, which is very convenient.

However, with this configuration, if you are receiving teletext using the 21-pin RGB input terminal and return to TV mode every time you change channels, you will not be able to transmit teletext. In order to watch teletext, it is necessary to perform a mode switching operation to switch to RGB mode, which is inconvenient.

Purpose of the Invention The present invention solves the problems of the conventional example as described above. Only when video mode and RGB input mode are selected, channel switching returns to TV mode, and input mode for text broadcasting etc. The purpose of the present invention is to provide a television receiver in which the mode does not change when switching channels when RGB mode is selected.

Structure of the Invention The television receiver according to the present invention has an output terminal of a control circuit whose output is at a low level when a mode is selected to receive information applied to a second input terminal such as for receiving teletext. is connected to the anode of the diode along with the output terminal of the pulse generation circuit when switching channels.As a result, when the above mode is selected, the mode switching circuit is not reset even if the channel switching operation is performed. It is possible to achieve the initial purpose.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In the figure, 1 is 6 that constitutes a mode switching circuit.
It is a forward counter, 2 is a circuit for generating a defective pulse generated when switching channels, and 3 is a circuit for generating a reset pulse when the power is turned on. Diodes 4, 5, and 6 constitute an OR circuit,
Each cathode of diodes 4, 5, and 6 is connected to counter 1.
connected to the reset terminal of the counter 1
, , , terminals are used as mode switching control voltages. Further, the terminal of the counter 1 is a mode switching pulse input (rotation pulse) terminal. The counter 1 terminal is RGB
This is a reset pulse output terminal for changing the mode to TV mode. Diode 4 is for resetting when switching modes, diode 5 is for resetting when power is turned on, and diode 6 is for resetting when switching channels, forming an OR circuit. It is assumed that when the counter 1 is reset, the TV mode is entered.

The anode terminal of diode 12 has a high level "H" in RGB 8 pin input mode and low level "L" in other modes, and the anode terminal of diode 13 has a low level "L" in RGB mode, and in other modes. In this mode, a high level "H" control voltage is applied. diode 12,
13 constitutes an OR circuit, and both cathodes are connected to the base of transistor 9 via resistor 11.

The collector output terminal of the transistor 9 is connected to the base of the transistor 7, and the collector output terminal of the transistor 7 is connected to the diode 6 together with the output terminal of the defective pulse generation circuit 2 at the time of channel switching.
connected to the anode of

Therefore, a low level "L" control voltage is applied to the base of the transistor 9 in the RGB 21 pin input mode for teletext broadcast reception, and a high level "H" control voltage in other modes. RGB21
In the pin input mode, the base of transistor 9 is at a low level "L", so the collector is at a high level "H", and therefore the collector of transistor 7 whose base is connected to the collector of transistor 9 is at a low level. It becomes "L" and turns off the reset circuit when switching channels.

i.e. RGB21 to receive teletext
When in pin input mode, switching channels does not return to TV mode; in other modes, switching channels returns to TV mode, allowing the initial purpose to be achieved.

In the figure, 8 is the collector load resistance, 10
is the guaranteed resistance of the transistor 9 when it is off.

Effects of the Invention As described above, according to the present invention, by preventing the reset operation of the mode switching circuit from being performed in the RGB 21-pin mode, the mode returns to the TV mode even if the channel is switched in the RGB 21-pin mode. There is no need to change the channel in any other mode, and then you can return to TV mode, which is convenient in practice.

[Brief explanation of drawings]

The figure is a circuit diagram of a television receiver according to an embodiment of the present invention. 1...Counter, 2...Channel switching pulse generation circuit, 4, 5, 6, 12, 13...Diode, 7, 9...Transistor.

Claims (1)

[Claims] 1 TV mode for displaying television signals;
Video mode that displays video signals from external video signal sources, and displays text and graphic information from external sources.
A television receiver that sequentially selects RGB modes and displays each signal has a mode switching pulse input terminal and a reset input terminal,
Every time a mode switching pulse is input to the above mode switching pulse input terminal, a mode switching control voltage is generated to sequentially select TV mode, video mode, and RGB mode, and when a mode switching pulse is input in the RGB mode selection state, the mode A counter that applies a switching control voltage to the reset input terminal via the first diode to reset to TV mode, a channel switching deficit pulse generation circuit that generates a deficit pulse when switching channels, and a circuit that generates a deficit pulse when switching channels; A control circuit that outputs a low-level control signal and a high-level control signal in modes other than RGB mode, and the output terminal of the control circuit is common to the output terminal of the day-to-day pulse generation circuit when switching channels. A television receiver characterized in that the counter is connected to the reset input terminal of the counter via a second diode.