JPS61274584A - Switching unit for video signal - Google Patents

Abstract

PURPOSE:To reduce the number of control lines between a cross point and a control circuit and that of the control circuit by making the cross point on or off according to the AND condition of two cross point control input signals. CONSTITUTION:As for a cross point 10, when either one of control input terminals 16 or 19 is 'L', a diode 17 or a diode 18 is turned on and base voltage of a transistor 14 is reverse-biased and the cross point 10 is turned off. At such a case, the cross point 10 is turned on according to the AND condition in each 'H' level of the terminals 16 and 19.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a television studio transmission system, and particularly to a semiconductor video signal switching device.

[Prior Art] A conventional video signal switching device of this type is shown in FIG. Multiple cross points 10.20.30 as shown in Figure 3
．． In the semiconductor video signal switch 40, for example, when cross point 10 is "on", cross points 20, 30, and 40 are in a reverse biased state and in an off state. (Each cross point in Figure 3) 10
．． 20, 30, and 40 are the same, and will be described here with reference to crosspoint 10. A video signal is supplied from an input terminal 11, passes through a transistor 12, and is applied to the base of a switching transistor 14α. Here, a predetermined bias, for example OV, is applied to the base of the transistor 12. The emitter of transistor 14 is connected to output terminal 15. The diode 17 is turned on and off by control input from the control input terminal 16. In the figure, when the control input terminal 16 is at LOW level, the diode 17
is turned on, the base potential of the transistor 14 is reverse biased, and the cross point 10 is turned off. When control input terminal 16 is at high level, diode 1
7 is turned off, the base potential of the transistor 14 is forward biased, and the cross point 10 is turned on. Also at cross points 20, 30, 40, input terminal 21
．． 31.41. Switching transistor 24.34.44
, control input terminals 26, 36, and 46 are provided, respectively. Each cross point 1O120, 30, 40 is connected to a negative voltage power supply -■ through a resistor 100. Note that I3.23.33.43 is a resistor. FIG. 4 shows a case where a matrix video signal switch is constructed using a plurality of rows of the video signal switch of FIG. 3. This matrix video signal switcher includes Xi, X2. , , 71 receives n input video signals of Xn.

It constitutes an nXm video switch that switches to m output of 12-yn. This nXm video signal switcher is nXm
Each crosspoint control input terminal is connected by nXm control lines from a control circuit, and the control lines and each crosspoint are controlled on a one-to-one basis. [Problems to be solved] The conventional video signal switching device described above has a cross point and a cross point of ON10F.
The control circuits for controlling the crosspoints have a one-to-one correspondence, and the number of control lines required to control the crosspoints is equal to the number of crosspoints to be controlled, which becomes quite large as the scale of the video signal switch increases. There was a problem with that.

Solution to Problem c] The present invention has been made to solve the above problems, and provides a video signal switching device that can significantly reduce the number of control lines and control circuits between cross points and control circuits. We aim to provide the following.

To this end, the present invention provides a video signal switching device that inputs a plurality of video signals to a plurality of crosspoints and outputs a selected video signal, which has two control inputs as the crosspoint α control input. control signal AN
The present invention provides a video signal switching device characterized by turning on and off cross points according to conditions D.

[Example] Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the present invention.

When compared with the diagram showing the conventional example in Fig. 3, the control input terminal 1
9 and a diode 18 are added and connected in parallel to the conventional control input terminal 16 and diode 17. Cross points 10, 20, 30, and 40 also have the same configuration, and will be explained here with reference to cross point IO. When one of the control input terminals 16 and 19 of the cross point 10 is at a LOW level, the diode 17 or 18 is turned on, the base potential of the transistor 14 is reverse biased, and the cross point is turned off. That is, to turn on the crosspoint, use the control input terminal 16.
Both of the control input terminals 16 and 19 need to be at high level, and are turned ON by the AND condition of the two control input terminals 16 and 19.

FIG. 2 shows a case where a matrix video signal switch is constructed using a plurality of rows of video signal switchers shown in FIG. 1. When this matrix video signal switcher configures an nXm video switcher, the two control input terminals of the nXm crosspoints are connected in a vertical and horizontal matrix, and common control for m vertical and n horizontal signals. connected to the line. To turn on the cross point, when both the vertical and horizontal control lines are at high level, the cross point is turned on. That is, in order to control each crosspoint, m+n control lines are sufficient, and the number of control lines between the crosspoint and the control circuit is only m+n.

[#5 Effect of Brightness] As described above, the present invention provides a video signal switching device that inputs a plurality of video signals to a plurality of crosspoints and outputs a selected video signal, in which two inputs are used as control inputs of the crosspoints. The video signal switch has two control inputs and turns the crosspoint on and off based on the AND condition of two control signals, so the two control inputs can be used as a common control line, so the crosspoint This has the effect of greatly reducing the number of control lines between control circuits and the number of control circuits.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram showing an example using a plurality of the circuits shown in FIG. 1, FIG. 3 is a circuit diagram showing a conventional example, and FIG. FIG. 4 is a circuit diagram showing an example in which a plurality of the circuits shown in FIG. 3 are used. 11.21, 31.41. ,,input terminal 15.25.3
5.45. ,,output terminals 16, 19, 26, 29, 36
, 39.46.49. ,,control input terminal

Claims (1)

[Claims] In a video signal switching device that inputs a plurality of video signals to a plurality of cross points and outputs a selected video signal, it has two control inputs as the cross point α control input, and according to an AND condition of the two control signals. A video signal switch that turns cross points on and off.