JPS59147576A - Television receiver - Google Patents

Abstract

PURPOSE:To switch automatically TV broadcast and external information by switching automatically an incorporated input changeover switch to an external signal source side when a power supply is turned on the external signal source by using a synchronizing signal. CONSTITUTION:An input changeover circuit 10 is provided to a TV receiver 4. An external information signal 2 from an external signal source 1 comprising each color signal, a horizontal synchronizing signal and a vertical synchronizing signal is given to an external information input terminal 3. A signal having a prescribed voltage so long as the signal 7 is inputted and the power of the signal source 1 is given by a retriggerable monostable multivibrator 8 is formed by the signal 7 by using the horizontal or the vertical synchronizing signal 7, the signal is applied to the circuit 10 as a control signal 9, and the switch is changed over automatically to the signal source 1 at the input from the signal source 1. Thus, the automatic switching between the TV broadcast and the external information is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION This invention relates to a television receiver capable of inputting and displaying character information and graphic information from an external signal source such as a personal computer.

Conventional configuration and its problems At present, television receivers are equipped with an input terminal that can input external information, such as a signal from a personal computer, and an input switch for switching between the television signal and the external information. By providing a switch circuit and operating the input selector switch circuit, information from a personal computer is displayed on a cathode ray tube in place of television broadcasting. In this case, it is cumbersome to manually switch between television broadcasting and external information.

OBJECTS OF THE INVENTION An object of the present invention is to provide a television receiver that can automatically switch between television broadcasting and external information.

Structure of the Invention The television receiver of the present invention receives a horizontal synchronization signal or a vertical synchronization signal from input signals (RGB signals, horizontal and vertical synchronization signals) separately supplied from an external signal source such as a personal computer. When the external signal source is turned on, the built-in input selector switch is automatically switched to the external signal source.

DESCRIPTION OF THE EMBODIMENTS FIG. 1 shows a block diagram of an input switching circuit of a television receiver with an external signal input terminal.

In FIG. 1, an external information signal 2 enters an external information signal input terminal 3 of a television receiver 4 from an external signal source (personal computer) 1.

External information signal 2 is red (R), green (G), blue (B
), a horizontal synchronization signal, and a vertical synchronization signal, each of which is supplied through separate cables. Here, an external information signal 5 such as red, green, or blue is applied to an input switching circuit 10 together with a television signal 6 such as red on the television side, and is switched by this input switching circuit 10 to output a television to a cathode ray tube. The signal 6 or the external information signal 5 from the external signal source 1 side is displayed. The input switching circuit 10 can be constructed using a changeover switch IC, a transistor, etc., but whether it is an IC or a transistor, a switching control signal 9 is required to control switching. As this control signal 9, it is sufficient to apply a constant voltage to distinguish between receiving a normal television broadcast and inputting an external information signal.

Therefore, in this embodiment, the horizontal synchronization signal or vertical synchronization signal 7 input from the external signal source 1 is used, and the monostable multivibrator 8, which can be retriggered by this synchronization signal 7, is used to turn on the power of the external signal source 1. As long as the horizontal or vertical synchronizing signal 7 is input, a signal with a constant voltage is generated, and this signal is added to the input switching circuit 1 as the control signal 9. When input from the external signal source 1, the signal is automatically switched to the external signal. I am trying to switch it to the source 1 side.

FIG. 2(A), Q3) shows the waveforms of the horizontal synchronizing signal and vertical synchronizing signal output from the external signal source 1. Note that the period T8 of the horizontal synchronization signal is approximately 63 Sμseo, and the period TV of the vertical synchronization signal is approximately 16.7 msec.

For example, when controlling using a horizontal synchronizing signal, the horizontal synchronizing signal TH is approximately 635 μSea. Although there are slight differences depending on the external signal source 1, if the circuit constants are determined so that the monostable multivibrator 8 has an unstable period of 640 μSeQ or more as shown in Fig. 3 (A), it is possible to avoid repeated input. Since the period 'rH of the horizontal synchronizing signal is about 635μ8eQ, the output of the monostable multivibrator 8 can continuously obtain a voltage at a constant level (unstable state) as long as the horizontal synchronizing signal is input. Also, when using a vertical synchronizing signal, if the monostable multivibrator 8 is set to the period TV1 of the vertical synchronizing signal, that is, about 16.7 m5ec or more, as shown in Fig. 3 (B), in the case of a horizontal synchronizing signal, Similarly, a constant level voltage can be obtained continuously, and by using this signal as the control signal 9, switching between the TV side and the external signal source 1 side can be automatically performed when the external information signal is input. It becomes possible to switch to the 1 side. That is, it is possible to automatically switch to the external signal source 1 side in response to power-on of the external signal source 1.

Effects of the Invention (5) As described above, according to the television receiver of the present invention, it is possible to automatically switch between television broadcasting and external information from an external signal source such as a personal computer, which is extremely effective in practical use. It's convenient.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a television receiver according to an embodiment of the present invention, and FIGS. 2(A), Q3) and 3(A), 03) are waveform diagrams for explaining the operation, respectively. It is. 1... External signal source, 4... Television receiver, 8
... Monostable multivibrator, 10... Input switching circuit (6) Fig. 1 Tl-1 Fig. 3 Fig. 2

Claims (1)

[Claims] an external information signal input terminal that inputs an external information signal from an external signal source; an input switching circuit that selects and outputs either the television signal or the external information signal input from the external information signal input terminal; The external information signal is triggered by a synchronization signal included in an external information signal inputted from the external information input terminal, has an unstable period longer than the synchronizing signal, and outputs the external information signal by an output during this unstable period. A television receiver comprising a retriggerable monostable multivibrator controlling an input switching circuit.