JPH0145186Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a test pattern signal generator (hereinafter referred to as a TP signal generator), and particularly to a TP signal generator suitable for use in a video tape recorder (hereinafter referred to as a VTR).

Some VTRs are equipped with a TP signal generator to adjust the television receiver used for playback prior to playing back recorded images recorded on a videotape.

Figure 1 shows the main parts of a conventional TP signal generator and switching circuit installed in a VTR. +B connected to power supply,
A TP signal output terminal 1B is connected to one input terminal TPSG of a signal switch 2A. Signal switch 2
A selects either the TP signal or the video signal played by the VTR and input to the other input terminal VIDEO IN and applies it to the video signal input terminal of the RF modulator (not shown). It is. The signal applied to the RF modulator is converted into a signal of an empty channel of television broadcasting and is applied to the antenna terminal of the television receiver. Reference numeral 3 denotes a synchronization signal generating section comprising a crystal oscillator 3A and the like.

In the circuit shown in FIG. 1, the signal switch 2A and the power switch 2B are switched in conjunction. That is,
When applying a TP signal to the RF modulator, the power switch 2B is turned ON to operate the TP signal generation circuit 1, and at the same time, the signal switch 2A is switched to one input terminal TPSG to output the TP signal. Also, when adding the video signal played by a VTR to the RF modulator, use the power switch 2B.
At the same time as switching to the OFF state and stopping the operation of the TP signal generation circuit 1, the signal switch 2A is switched to the other input terminal VIDEO IN side to output a video signal.

In such a configuration, two switching devices, the signal switching device 2A and the power switching device 2B, are mechanically linked, or a method is used in which one switching device is provided with multiple sets of switching terminals. . However, in either method, it is necessary to determine the placement of one switch depending on the placement of the other switch, and this restriction makes the pattern of the printed circuit board that makes up the TP signal generator long and complicated. The size of the device has grown over time, which has hindered miniaturization of the device.

It is an object of the present invention to provide a TP signal generator that improves the problems of the prior art, facilitates the setting of printed circuit board patterns, has good operability, and can be miniaturized.

Therefore, the TP signal generator according to the present invention has a first input terminal that inputs a video signal, a second input terminal that inputs a TP signal, and selects one of the two signals and sends it to an RF modulator. A signal switcher equipped with an output terminal to output, and a TP
An emitter and a collector are interposed in series between a TP signal generation circuit that generates a signal, a power supply terminal of the TP signal generation circuit, and a power supply, and the base is connected to the second input of the signal switch via a resistor. It includes a switching transistor connected to the terminal, and a resistor connected between the output terminal of the signal switching device and ground.

In this configuration, the second
When the input terminal and output terminal of It will be done. Then, the TP signal generation circuit operates. On the other hand, when the signal switching device is operated to connect the first input terminal and the output terminal, the switching transistor becomes non-conductive, and the TP signal generation circuit is no longer supplied with power and stops operating.

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 2, the same components as those in the conventional example shown in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

The configuration shown in FIG. 2 differs from the configuration shown in FIG. 1 in that a switching circuit 11 is provided in place of the power switch 2B. Switching circuit 1
1 consists of a resistor 11A and a PNP type switching transistor 11B.
The base terminal of B is connected to one input terminal TPSG of the signal switch 2A via the resistor 11A, the emitter terminal is connected to the +B power supply, and the collector terminal is connected to TPSG.
They are each connected to the power supply terminal 1A of the signal generation circuit 1. Further, resistors 13 and 14 are connected in series between the output terminal of the signal switch 2A and the ground, and are connected to the RF modulator via a capacitor 15 connected to the connection point between the resistors 13 and 14. It is configured.

In the configuration shown in Figure 2, when playing a VTR, the signal switch 2A is set to VIDEO as shown in Figure 2.
When switched to the IN side, the video signal is output to the RF modulator, and when switched to the TPSG side, the TP signal generation circuit 1 operates and the TP signal is supplied to the RF modulator. That is, when the signal switch 2A is switched, not only a signal is selected, but also the switching circuit 11 is switched between ON and OFF states in conjunction with the switching, and the switching circuit 11 turns on and off the TP signal. The generating circuit 1 is controlled into an operating state and a stopped state.

Note that when the switching circuit 11 is in the ON state, the base current of the transistor 11B is blocked by the resistor 11A and the capacitor 15, so that it has no effect on the TP signal output to the RF modulator.

As described above, according to the present invention, the signal switch 2
The operation of the TP signal generation circuit 1 can be controlled simply by operating A, and the restrictions on the placement of the switching circuit are greatly reduced, so the printed circuit board pattern can be shortened and the device can be made smaller. . Also,
Since the power supply switching device is an electronic switching device, durability is increased and a highly reliable test pattern signal generating device can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a conventional technique, and FIG. 2 is a circuit diagram showing an embodiment of the present invention. 1...Test pattern signal generation circuit, 2A...
Signal switch, 11...Switching circuit, 11A, 14...
...Resistor, 11B...Switching transistor.

Claims (1)

[Scope of utility model registration request] A first input terminal for inputting a video signal, a second input terminal for inputting a test pattern signal, and an output terminal for switching and selecting one of the second signals and outputting the selected signal to an RF modulator. A signal switching device, a test pattern signal generation circuit that generates the test pattern signal, and an emitter and a collector interposed in series between the power terminal and the power supply of the test pattern signal generation circuit, and the base is a resistor. 1. A signal generating device for a test pattern, comprising: a switching transistor connected to the second input terminal via a resistor; and a resistor connected between the output terminal and ground.