JPH0136754B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a television receiver having a function of switching and displaying a demodulated output signal of radio waves received by a television receiver circuit and a color signal input from an external additional device at a monitor input terminal. It is something.

Conventionally, when a television receiver is provided with an external RGB signal input terminal and an external additional device is connected to it, switching between internal and external signals is done by a mechanical switch, or by a device other than the television receiver. Switching was performed using one of the following methods: an electronic switch using a control signal from an externally connected device. However, in the former case, high-speed switching is not possible, and in the latter case, the problem of high-speed switching can be solved, but if the user forgets to turn off the power switch of an externally connected device, etc. The problem is that the state is retained. Therefore, in the case of the latter configuration, even though the user turns on the power to the television receiver, neither the internal demodulated signal of the television receiver nor the display signal from the externally connected device will be displayed on the screen. There were also problems such as not being displayed on the screen, giving the user the misunderstanding that the device was malfunctioning.

SUMMARY OF THE INVENTION Therefore, the present invention provides an apparatus that can automatically solve the above-mentioned disadvantages of the conventional apparatus and with a minimum number of control input terminals. below,
An embodiment will be described with reference to drawings.

First, FIG. 1 is a block diagram of a television receiver. A television receiver circuit 1 receives television radio waves, selects channels, etc., and supplies the received signal to a signal demodulation circuit 2. In the signal demodulation circuit 2, the red and
The demodulated green and blue color signals r, g, and b are supplied to the signal switching circuit 3. In addition, red, green, and blue color signal inputs r', g', and b' for display from an external additional device such as a teletext receiver supplied to terminals 4, 5, and 6 are sent to an external signal amplification circuit 7. The signal is supplied, amplified, and supplied to the signal switching circuit 3. In the signal switching circuit 3, one of the signals from the above two systems is selected and outputted as color signals R, G, B for display, and is supplied to the signal output circuit 8, where it is amplified and sent to a cathode ray tube, etc. is supplied to the display element 9 for display.
Reference numeral 10 denotes a remote control signal receiving circuit whose control output is supplied to the television receiving circuit 1 for channel selection and the like. Reference numeral 11 denotes an internal control signal supply circuit, into which the pulse signal x from the television receiver circuit 1 is input, converted into a control signal, and supplied to the control signal processing circuit 12. The control signal processing circuit 12 converts the signal into a signal necessary for driving the switching operation of the signal switching circuit 3, and supplies the signal to the signal switching circuit 3.
In addition, external control signal input terminal 1 can be input from external additional equipment.
The external control signal x' inputted to 3 is connected to the output terminal of internal control signal supply circuit 13.

Next, FIG. 2 shows a detailed block diagram within the broken lines in FIG. 1. Here, 14, 15, 16 are input terminals for r, g, b demodulated color signals from the television receiver circuit 1, 17 is an input terminal for an internal control signal x, 1
8, 19, and 20 are R, G, and B respectively constructed by electronic switch circuits such as analog gates.
21, 22, 23 are amplifier circuits for external color signals r', g', b', respectively; 24 is a T flip-flop controlled by an internal control signal x; 25 is a switching transistor. .

The switching operation is such that when the output of the control signal processing circuit 12 is at a low level, the color signals r, g, b from the television receiver circuit 1 are output to the color signal output terminals 26, 27, 28.
is output to. In addition, when the level is high, the color signals r', g', b' from the external additional equipment are sent to the color signal output terminal 26,
27 and 28. Control signal processing circuit 12
The operation is level conversion and waveform shaping to drive the above-mentioned signal switching, and the phase relationship between the input and output is in-phase. T flip flop 24
automatically outputs Q when the TV receiver is turned on.
is set to be at a high level.

FIG. 3 shows a waveform diagram of each part of FIG. 2. Section A is the period from when the power of the television receiver is turned on until the first internal control signal x is generated. First, the Q output of the T flip-flop 24 is set to be at a high level when the power is turned on, so it is at a high level. At this time, since the base of the transistor 25 is at a high level, the transistor 25 is turned on, and the collector becomes a low level regardless of the external control signal x' from the terminal 13. Therefore, the control signal processing circuit 12
The outputs of R, R, and R from the signal switching circuits 18, 19, and 20 also become low level, as described above.
As G and B, color signals r, g, and b from the television receiver circuit 1 are output. Therefore, during this period A, the influence of the external control signal x' disappears,
Only the demodulated color signals r, g, and b are output, and a television reception screen is displayed.

Next, section B is a section from when the first pulse x ₁ of the internal control signal x is applied until when the next pulse x ₂ is applied. At this time, the T flip-flop 24 is first triggered by the internal control signal _x1 , and its Q terminal output becomes low level. Therefore, the transistor 25 is turned off because its base becomes a low level, and its collector is connected to the terminal 1.
When the external control signal from 3 appears as it is, an external control signal R, G, B are synchronized with external control signal x'
While x′ is at a high level, the color signal from the external additional device is
r', g', and b' are output, and while x' is at a low level, color signals r, g, and b from the television receiver circuit are output. Thus, in section B, the external control signal
Signal switching circuits 18, 19, and 20 are controlled by x'.

Furthermore, section C is a period after the second pulse _x2 of the internal control signal x. At this time, the operation of each circuit is the same as in section A.

Thereafter, the above switching operation is repeated every time a pulse of the internal control signal x is output until the television receiver is powered off.

As described above, according to the configuration of the present invention, it is possible to switch multiple color signals at high speed, and moreover, it is possible to output only the color demodulated signal of the television broadcast, regardless of the external control signal when the television receiver is turned on, etc. It can be switched so that it can be displayed as follows. As a result, the problem of no image being displayed on the screen of the receiver when the power is turned on will be eliminated. Further, internal control signals can be applied by a remote control or the like, and electronic control can be performed.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a television receiver according to an embodiment of the present invention, FIG. 2 is a detailed block diagram of its main parts, and FIG. 3 is a waveform diagram of each part thereof. 1... Television receiver circuit, 2... Color demodulation circuit, 3, 18, 19, 20... Signal switching circuit,
4, 5, 6...Input terminal for external color signal, 7, 2
1, 22, 23,...external signal amplification circuit, 8...
Signal output circuit, 9... Display element, 10... Remote control receiving circuit, 11... Internal control signal supply circuit, 12... Control signal processing circuit, 13...
Input terminals for external control signals, 14, 15, 16...
Input terminal for color signal, 17...Input terminal for internal control signal, 24...T flip-flop, 25...Transistor, 26, 27, 28...Output terminal for color signal.

Claims (1)

[Claims] 1. A switching circuit that inputs the demodulated output signal from the television receiver circuit and the display color output signal from the external additional equipment, selectively switches and outputs both signals, and a pulse signal output from the television receiver circuit. an internal control signal supply circuit comprising means for emitting an output signal while maintaining the output level until the next pulse signal is input, and a switching element that is turned on and off by the output signal;
An external control terminal to which an external control signal from the external additional device is applied is provided, the external control terminal is connected to the output terminal of the switching element, this connection point is connected to the input terminal, and the internal control signal and external control signal are connected to the output terminal of the switching element. A control signal processing circuit is provided which generates a binary output signal according to the switching control signal, and this binary output signal is added to the switching circuit as a switching control signal, and the switching circuit selectively outputs the demodulated output signal and the display color output signal. The internal control signal supply circuit controls the switching circuit via the control signal processing circuit from when the power is turned on until the first pulse signal is input. A television receiver characterized in that the television receiver is controlled so that the demodulated output signal is outputted from an output end.