JPS58207778A - Television receiver - Google Patents

Abstract

PURPOSE:To prevent a power supply of an external device from being left turned on, by outputting a chrominance signal from a television receiving circuit independently of any of external control signal at the application of power supply, in the television receiver having a switching display function. CONSTITUTION:When an output of a control signal processing circuit 12 is a low level, chrominance signals (r, g, b) from a television receiving circuit are outputted to chromoiance signal output terminals 26-28. When the output is a high level, chrominance signals r', g', b' from the external accessory devices are outputted to the chrominance signal output terminals 26-28. Since a T flip-flop 24 is set so as to obtain an output Q of high level automatically at the application of power supply, a collector of a transistor 25 is a low level independently of the external control signal x' from a terminal 13, an output of the control signal processing circuit 12 is also a low level, and the chrominance signals r, g, b from the television receiving circuit are outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides 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. - to do.

Conventionally, when a television receiver is provided with an external RGB signal input terminal and an external additional device is connected to it, the internal and external signals can be switched by: (1) switching by a mechanical switch; (2) the television; Switching was performed using an electronic switch using a control signal from an externally connected device other than the television receiver. 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.

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

First, FIG. 1 is a block diagram of a television receiver. 1
is a television receiver circuit, which receives television radio waves.
The channel selection, etc. is performed, and the received signal (i) is supplied to the signal demodulation circuit 2.1.; In the bow-tuning circuit 2, fL, /1., is necessary for displaying each JL on the screen.

Green and blue color signals r+ q! ” and supplied to the signal switching circuit 3. In addition, red, green, and blue color signals for display from external additional equipment such as a teletext receiver supplied to terminals 4.5-.6 are Inputs r', q', and b' are supplied to an external signal amplification circuit 7, amplified, and supplied to a signal switching circuit 3.In the signal switching circuit 11 and path 3, one of the two systems described above is input. One of the 2t signals is selected and output as display color signals R, G, B, supplied to a signal output circuit 8, amplified) and supplied to a display element 9 such as a cathode ray tube for display. .1o is a remote control No. 4 receiving circuit, the control output of which is supplied to the television receiving circuit 1 for channel selection 19.11 is an internal 8Jll all
In the signal supply circuit, the pulse signal
is input and converted into a control signal to the control signal processing circuit!
Supplied to circuit 12. In the control signal processing circuit 12, the signal is converted into a necessity signal and supplied to the signal switching circuit 3 in order to drive the switching operation of the signal switching circuit 3.

1, the external control signal X' input from the external additional device to the external control signal input terminal 13 is sent to the internal control signal supply circuit 13
connected to the output terminal of

Next, FIG. 2 shows a detailed block diagram within the broken line in FIG. 1. Here, 14, 16, and 16 are the television receiver circuit 1
input terminal for the demodulated color signal of r+q+b from 17
18, 19, 20 are signal switching circuits for R, G, and B respectively constructed of electronic switch circuits such as analog gates; 21, 22.
23 is an amplification circuit for external color signals r', q', b', respectively; 24 is a T flip-flop controlled by an internal control signal X; and 26 is a switching transistor.

In this switching operation, when the output of the control signal processing circuit 12 is at a low level, the color signal "191b" from the television receiver circuit 1 is output to the color signal output terminals 26.2, 2B.
If the level is high, the color signal rz, q from the external additional equipment
/, bl is the color signal output terminal 26. :□27.
Output to 2B. The operation of the control signal processing circuit 16r is level conversion and waveform product multiplication for driving the above-mentioned signal switching, and the phase relationship between its input and output is in phase. The T flip-frog 24 is set so that the output O automatically becomes a high level state when the television receiver is turned on.

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-frog 24 is set to be high when the power is turned on, so it is at a high level. At this time, since the base of the transistor 26 is at a high level, the transistor 25 is turned on, and the collector becomes a low level regardless of the external control signal I' from the terminal 13. Therefore, the output of the control signal processing circuit 12 also becomes low level, and as described above, the signal switching circuits 18, 1
Color signal outputs R, G from 9 and 20.

B is the color signal r from the television receiver circuit 1.

q and b are output. Therefore, during this period A, the influence of the external control signal X' disappears, and only the demodulated color signals r, g, and b are output, and the television reception screen is displayed.

Next, section B is the first node x of the internal control signal
This is the period from when 1 is added until the next pulse x2 is added. At this time, 1 T flip frog 2
4 is triggered by the internal control signal x1 and its Q
The terminal output becomes low level. This is useless, transistor 2
6 is turned off because its base becomes low level, and the external control signal from terminal 13 is directly applied to its collector. As a result, an external control signal While X' is at a high level in synchronization with ', the color signal from the external additional device is
y'' is output, and while xl is at a low level, the color signal r+'J+b from the television receiver circuit is output.Thus, in section B, the external control signal X' causes the signal switching circuits 18, 19, 20 are controlled.

Furthermore, section C is the second pulse x2 of internal control signal
This is the period after. At this time, each circuit operates in section A.
is the same as

From then on, the internal control signal
The above switching operation is repeated every time a pulse is output.

As described above, according to the configuration of the present invention, high-speed switching of a plurality of colors '11+' is possible, and in addition, television
When the receiver is powered on, it is possible to switch so that only the color demodulated signal of television broadcasting can be output and displayed, regardless of the external control signal. Further, internal control signals can be applied by a remote control or the like, and electronic control is possible.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a television receiver according to an embodiment of the present invention, and FIG. 2 is a detailed block diagram of its main parts.
FIG. 3 is a waveform diagram of each part. 1...Television receiver circuit, 2...
Color recovery ku'+ path, 3.18, 19.20... Signal switching circuit, 4° 5.6... External color signal input terminal, 7, 21.22° 23. ...External signal amplification circuit, 8...Signal output circuit, 9...Display element, 1o...Remote control receiving circuit, 11...Internal Control signal supply circuit, 12...
... Control signal processing circuit, 13... Input terminal for external control signal, 14, 15.16... Input terminal for color signal, 17... Input terminal for internal control signal. input terminal,
24...T flip-flop, 25...
・Transistor, 26.27.28... Color signal output terminal.

Claims (1)

[Claims] The demodulated output signal from the television receiver circuit and the display color output signal from the additional equipment are added to the switching N path, selectively switched by the switching circuit and supplied to the display element, and the switching circuit An external control terminal to which a control signal is applied to switch the output of the display color signal from the additional device, and the switching circuit is connected to the television receiver circuit regardless of the control signal from the external control terminal. and an internal control signal supply circuit that switches to output only the demodulated output signal from the television receiver.