JPH10308883A - Video distribution amplifier and video distribution amplifier system using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a video image distribution amplifier where an input is in bridge connection, a termination resistor is automatically inserted and no special connector or the like is in use and a video image distribution amplifier system employing the amplifier. SOLUTION: A video signal source 5 gives a video signal to a video distribution amplifier 1-1 through a coaxial line via an input receptacle IN and the video signal is given to an input receptacle IN of a video distribution amplifier 1-2 via a coaxial line (g) from a receptacle IN' as a bridge input, a switch S is closed in the video distribution amplifier 1-2 and a termination resistor R terminates the coaxial line. An coaxial outer sheath of the bridge output coaxial receptacle IN' is not connected to the ground in the inside of the video distribution amplifiers 1-1, 1-2, but its level is boosted to a voltage Vcc via a boosting resistor (r). When the video distribution amplifiers 1-1, 1-2 are in bridge connection by the coaxial line (g), the coaxial cable outer sheath is connected to the ground and an input voltage of a control circuit 3 is 0V, then the control circuit 3 detects the bridge connection and disconnects the termination resistor R.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video distribution amplifier and a video distribution amplifier using the same, and more particularly to a video distribution amplifier for business use such as broadcasting and a video distribution amplifier using the same.

[0002]

2. Description of the Related Art When transmitting a baseband (for example, an NTSC television video signal having a basic spectrum of 0 Hz to 4.2 MHz) over a relatively short distance, a characteristic impedance of 75Ω is usually used. Transmission with a coaxial cable with.

[0003] For example, in the case of transmission in a broadcasting station studio, a 75Ω connector usually called a BNC connector is used as a coaxial connector, and a receptacle (plug seat) fixed on a panel of the apparatus is a female type. The plug attached to the inserted coaxial cable is a male type.

When inputting video signals to a plurality of devices, one device is provided with two input connectors (receptacles) and these two input receptacles are connected in the device, and the input video signals are not connected. There is a method of connecting a coaxial cable to the other receptacle, connecting this to the input receptacle of the next device, repeating this, and finally terminating (for example, with a 75Ω resistor). Call.

[0005] If the input impedance of the above-mentioned plurality of devices is sufficiently large compared to the characteristic impedance of the coaxial transmission line (for example, 75Ω), if the length of the coaxial transmission line is not so long, the coaxial transmission is possible even if bridged. Almost no loss of road characteristics.

In addition to the television video signal coaxial transmission, a bridge connection may be used in a personal computer system, for example, in a SCSI bus used to connect a scanner or a hard disk device to a personal computer. .

In broadcasting studio studies, it is necessary to distribute one (television) video signal input to various locations. Conventionally, as shown in FIG.
One video signal input is connected to the input IN of the video distribution amplifier 1-1 using one video distribution amplifier 1-1 and 1-2,
In the video distribution amplifier 1-1, a signal is input to a video distribution amplifier (VDA) 2 having a sufficiently high input impedance, and also in the video distribution amplifier 1-1, a coaxial cable is connected from a connected connector IN 'through a bridge connection. g, the signal is input to the video distribution amplifier 1-2, and the termination (resistance) plug 4 is connected to the connector IN 'of the video distribution amplifier 1-2 in the same manner, whereby the coaxial transmission line is terminated.

The image distribution and amplification device 2 shown in FIG. 3 is depicted as having a high impedance and two 75Ω outputs (some have more than two outputs). Therefore, the video distribution amplifier 1- 1 shown in FIG.
1 and 1-2 each have six 75Ω outputs OUTa-f, and the video distribution amplifiers 1-1 and 1-2 have a total of twelve 75Ω outputs OUTa-f.

In the case of the input bridge connection of the conventional video signal device as shown in FIG. 3, it is necessary to securely terminate the coaxial transmission line, for example, by attaching a terminating (resistor) plug. If not, there is a problem that video signal characteristics are seriously affected.

Japanese Unexamined Patent Publications Nos. Hei 3-187589 and Hei 4-299721 propose an automatic termination method in the case of bridge connection.

[0011]

Problems to be Solved by the Invention
No. 9 discloses that when a video signal of a television interphone system is transmitted in a two-wire system by bridge connection, a loop is formed by two signal transmission lines, a direct current is supplied to the loop, and when this direct current is detected, To automatically remove the terminating resistor inside its own device, board, unit, etc., judging that it is terminated by the device, board, unit, etc. connected by bridge connection after the device, board, unit, etc. Has been proposed. However, this method is a special method as compared with the coaxial transmission of a normal video signal, and cannot be applied to the coaxial transmission of a normal video signal.

Japanese Patent Application Laid-Open No. Hei 4-299721 discloses SC
When bridging a terminal device of a computer with an SI bus, an electric contact is provided on an outer surface of the SCSI receptacle,
There has been proposed a method of controlling the connection of the terminating resistor by short-circuiting the electrical contacts of the receptacle with the metal case of the SCSI plug when the SCSI plug is inserted. However, in this case, there is a problem that a special connector (receptacle or plug) is required.

It is an object of the present invention to bridge the inputs,
An object of the present invention is to provide a video distribution amplifier which does not use a special connector or cable, and a video distribution amplifier including the same, which can automatically insert / release a terminating resistor when necessary.

[0014]

According to the present invention, there is provided an image distribution amplifier comprising: a first coaxial connector for inputting a video signal; a second coaxial connector for bridge-outputting the input video signal;
A video distribution amplifier including a video distribution element, wherein a coaxial jacket side of said second coaxial plug seat is always insulated and a coaxial jacket side of said second coaxial plug seat is grounded externally. And a terminating means for terminating the terminating resistor with the output of the bridge detecting means.

Further, the bridge detecting means lifts the coaxial jacket side of the second coaxial plug seat to a logic power source via a resistor and connects the coaxial jacket side of the second coaxial plug seat to the bridge. When the connection is grounded at the first coaxial socket of the video distributing amplifier of the next stage, the voltage on the coaxial jacket side of the second coaxial plug seat lifted to the logic power supply via the lifting resistor is also increased. Is configured to detect the bridge connection by reducing the number of bridge connections.

Further, the terminating means connects the switch contact and the terminating resistor connected in series between the core wire of the first or second coaxial plug seat and ground, and the bridge detecting means connects the bridge. Is detected, the switch contact is released.

A video distribution apparatus according to the present invention is characterized in that a plurality of the video distribution amplifiers are connected in a bridge.

The operation of the present invention is as follows. The two input connectors of the video signal to be bridged are distinguished into the input side and the (bridge) output side, the jacket (ground) side of the coaxial receptacle on the bridge output side is insulated, and the jacket of the coaxial line to be bridged is If the plug is not inserted into the coaxial receptacle on the bridge output side, the ground is set on the input side of the device to be connected next (for example, a video distribution amplifier).
Detects that the jacket side of the receptacle is not grounded and automatically inserts a terminating resistor.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of a video distribution amplifier and a video distribution amplification apparatus including the same according to the present invention, and the same parts as those in FIG. 3 are denoted by the same reference numerals. In FIG. 1, a video distributor / amplifier for business use in a broadcasting station or a production house or the like generally has several video distributors 1-1, 1-2 to 1 in one apparatus housing.
1-n (usually, for example, up to 6 to 8 units) are mounted, and the input side of a plurality of video distribution amplifiers in one device housing is usually input through a bridge connection.

The video distribution amplifying device according to the present invention in FIG. 1 also has a single device housing (FIG. 2 shows that the ground of the device housing is a common ground for each video distribution amplifier. (Not shown), a plurality of video distribution amplifiers 1-1, 1-2 to 1-n, a power supply circuit (not shown), video distribution amplifiers 1-1, 1-2 to 1-n and a power supply It is composed of a motherboard (not shown) in which board plugs for inserting circuits are provided, and wiring is provided between them.

The video distribution amplifier 1-1, for example, receives an input video signal, for example, a BNC receptacle IN, an input bridge output (for example, BNC) receptacle IN ′ for bridge connection on the video signal input side, )
A video distribution amplifying element (VDA) 2, a video signal output (six in the figure) OUTa to f (for example, having a feed impedance of 75Ω, of a BNC receptacle), a terminating resistor (for example, 75Ω) R, and a terminating resistor R It is composed of a switch S for turning on / off.

As shown in FIG. 2, the detailed operation of the input bridge connection unit according to the embodiment of the present invention is as follows: a video signal is distributed from a video signal source (internal impedance is, for example, 75Ω) 5 via a coaxial line (characteristic impedance, for example, 75Ω). Amplifier 1-1
To the video distribution amplifier 1-2 via the coaxial line g from the receptacle IN ′.
, The switch S is closed and the coaxial line is terminated by the terminating resistor R in the video distribution amplifier 1-2.

The video signal input coaxial receptacle (for example, BNC) IN of the video distribution amplifiers 1-1 and 1-2 is directly attached to the apparatus housing or the video distribution amplifiers 1-1 and 1-2, and is provided with a coaxial jacket (ground). ) Side is immediately grounded, and the core side is connected to the input terminal of the video distribution amplifier 2 and the core of the video signal input bridge output coaxial receptacle IN '. Video signal input bridge output coaxial receptacle IN '
Is not grounded inside the video distribution amplifiers 1-1 and 1-2, and is connected to a logic power supply (Vcc) via a pull-up resistor (for example, 10 kΩ) r. ; For example, 5V).

For example, the video distribution amplifier 1-
When the bridges 1 and 1-2 are connected in a bridge, the coaxial jacket of the coaxial line g is grounded at the input receptacle IN of the video distribution amplifier 1-2, and therefore, the coaxial jacket side of the bridge output receptacle IN 'of the video distribution amplifier 1-1. Is also grounded, and the input voltage of the control circuit 3 changes from the logic power supply voltage, for example, 5 V to 0 V (ground potential) inside the video distribution amplifier 1-1.
Therefore, the control circuit 3 detects that the video distribution amplifiers 1-1 and 1-2 are bridge-connected, automatically releases the switch S, and disconnects the terminating resistor R.

[0026]

As described above, according to the present invention, when the coaxial jacket side of the input bridge output of the video distribution amplifier is grounded, it is detected that the bridge connection has been executed, and the terminating resistor is automatically set. This has the effect of preventing the terminal from being separated and not being terminated by mistake, or from being terminated doubly.

[Brief description of the drawings]

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

FIG. 2 is a detailed explanatory diagram of a bridge connection unit according to the embodiment of the present invention.

FIG. 3 is a block diagram of a conventional video distribution and amplification device.

[Explanation of symbols]

 1-1 to 1-n video distribution amplifier 2 video distribution amplification element

Claims (4)

[Claims] 1. A video distribution amplifier comprising: a first coaxial connector for inputting a video signal; a second coaxial connector for bridge-outputting the input video signal; and a video distribution element, Bridge detecting means for detecting that the coaxial jacket side of the second coaxial plug seat is always insulated and that the coaxial jacket side of the second coaxial plug seat is bridged by being grounded externally; And a terminating means for releasing a terminating resistor at an output of the bridge detecting means. 2. The bridge detecting means lifts the coaxial jacket side of the second coaxial plug seat to a logic power source via a resistor, and connects the coaxial jacket side of the second coaxial socket seat to the bridge. When the connection is grounded at the first coaxial socket of the video distributing amplifier of the next stage, the voltage on the coaxial jacket side of the second coaxial plug seat lifted to the logic power supply via the lifting resistor is also increased. 2. The video distribution amplifier according to claim 1, wherein the video distribution amplifier is configured to detect the bridge connection when the power supply voltage decreases. 3. The terminating means connects the switch contact and the terminating resistor connected in series between the core wire of the first or second coaxial plug seat and ground, and the bridge detecting means connects the bridge. 3. The video distribution amplifier according to claim 1, wherein said video distribution amplifier is configured to release said switch contact upon detection of a video signal. 4. A video distribution amplifying device comprising a plurality of video distribution amplifiers according to claim 1, 2, or 3 connected in a bridge.