JP2553535B2 - Magnetic recording / reproducing device for monitoring - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a monitoring magnetic recording / reproducing apparatus used in financial institutions and the like.

2. Description of the Related Art In recent years, mainly in financial institutions such as banks, a monitoring device including a monitoring camera and a magnetic recording / reproducing device has been widely used as an unmanned monitoring security application. The surveillance camera and the magnetic recording / reproducing apparatus were connected by a cable or the like.

Problems to be Solved by the Invention However, with the development of surveillance devices, the knowledge of these devices by criminals has improved, and the lens of the hidden camera is covered, the pinhole camera for the door is clogged with foreign matter, and the like. There has been an incident in which a cable connecting the surveillance camera and the magnetic recording / reproducing apparatus was cut so that the crime scene could not be recorded by the magnetic recording / reproducing apparatus and a criminal act was performed. That is, in the conventional surveillance device, when the lens of the surveillance camera is covered, a dark screen is recorded, and when the cable is cut, no signal is recorded. It was a problem.

The present invention solves the above problems, and provides a monitoring magnetic recording / reproducing apparatus having a new function capable of realizing reliable security monitoring by connecting an output circuit to a notifying means or another security device. The purpose is.

Means for Solving the Problems In order to achieve the above object, a monitoring magnetic recording / reproducing apparatus of the present invention comprises a clamp circuit for maintaining a pedestal level of a video signal at a constant voltage, and a video signal voltage output from the clamp circuit. And a comparator that compares the reference voltage output from the reference voltage setting circuit to determine the brightness of the video signal,
And a hold circuit for holding the output signal of the comparator for a certain period of time and outputting a video brightness signal.

Operation With the above configuration, the brightness of the video signal output from the monitoring image pickup device is determined in the magnetic recording / reproducing device, and it is determined whether or not an abnormality has occurred in the monitoring image pickup device.

Embodiment A monitoring apparatus using a monitoring magnetic recording / reproducing apparatus according to an embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

In FIG. 1, reference numeral 1 is an image pickup device for monitoring, for example, a television camera (hereinafter referred to as TV camera), and an output side of the TV camera 1 is an input of a magnetic recording / reproducing device such as a video tape recorder (hereinafter referred to as VTR) 2. Connected to the side. An image recording circuit 3 records the image signal output from the TV camera 1 on the magnetic tape by the rotary head 4. Reference numeral 5 denotes a clamp circuit, which sets the pedestal level of the video signal to a constant voltage (0 V in this embodiment).
It is to be. Reference numeral 6 denotes a comparator, which compares the voltage of the video signal output from the clamp circuit 5 with a reference voltage set in advance by a reference voltage setting circuit 7 including resistors R ₁ and R ₂ to determine the video signal voltage as a reference. If the voltage is equal to or higher than the voltage, an H level signal is output. A hold circuit 8 holds the H level signal output from the comparator 6 for a certain period of time. Reference numeral 9 denotes a detection circuit, which outputs an H level signal when the video signal is input. Reference numeral 10 is an output circuit for performing logical operation processing on the output signals of the hold circuit 8 and the detection circuit 9 and outputting them. The output side of this output circuit 10, that is,
The output side of the VTR 2 is connected to the notification means 11 such as a buzzer.

The operation of the monitoring device configured as described above will be described below.

First, FIG. 2 is a time chart for determining whether the video signal is bright or dark. The operation when the video signal is a normal video signal such as the a signal and the lens of the TV camera is covered to capture a dark image. Will be explained. When the signal a from the TV camera 1 is input to the VTR 2, the signal a is input by the clamp circuit 5.
The pedestal level of the signal is set to 0V and becomes the b signal which is the positive input signal of the comparator 6. The negative electrode of the comparator 6 is set to the reference voltage (c signal) by the resistors R ₁ and R ₂ . The comparator 6 outputs an L level signal when the TV camera 1 captures only a dark image, and outputs an H level signal when a normal video signal is output (d signal). By holding the H level signal of the d signal by the hold circuit 8 for a certain period of time, it becomes a video brightness signal e (e signal). This e signal is TV
It becomes an H level signal when the camera 1 outputs a normal video signal, and becomes an L level signal when it outputs a video signal of a dark image.

Next, FIG. 3 is a time chart for determining the presence / absence of a video signal. In FIG. 3, the cable connecting the TV camera 1 and the VTR2 is disconnected from the normal video signal such as the f signal, and the video signal is no signal. The operation will be described. When the f signal is input from the TV camera 1 to the VTR 2,
The f signal is applied to the detection circuit 9, and the detection circuit 9 outputs an H level signal for a normal video signal and an L level signal for no signal. As a result, a video presence / absence determination signal (g signal) is formed.

The image brightness signal e and the image presence / absence determination signal g are output circuits.
10 is applied to the output circuit 11 and the output circuit 11 performs an exclusive logical product to inform
It is output to 11. That is, when the TV camera 1 outputs a normal video signal, the output circuit 10 outputs an L level signal, and the notification means 11 does not operate. When an image signal is not output from the TV camera 1 or an abnormality occurs in which only a dark signal is output, an H level signal is output from the output circuit 10 and the notification means 11 operates to make a notification.

According to the above-described embodiment, when the lens of the TV camera 1 is covered or the like, the video signal capturing only the dark part is input to the VTR 2, or the video signal is not output from the TV camera 1. Since the notification means notifies, it becomes possible to know that an abnormality has occurred from the state where the video signal is normally input in another security room, etc., and the reliability as a monitoring device is improved. is there.

Although the present embodiment has described the configuration in which the output side of the output circuit 10 is connected to the notification means 11 such as a buzzer, the output side of the output circuit 10 is a control device for controlling the operation of the crime prevention shutter. The same effect can be obtained even if the configuration is connected to the input side.

EFFECTS OF THE INVENTION According to the present invention, since it is possible to detect the case where a video signal capturing only a dark portion is applied from the monitoring imaging device to the magnetic recording / reproducing device, a notification unit or the like is provided on the output side of the magnetic recording / reproducing device. By connecting, the monitoring ability can be improved. That is, according to the present invention, it is possible to provide a magnetic recording / reproducing apparatus for monitoring which realizes a new function capable of surely performing security monitoring.

[Brief description of drawings]

FIG. 1 is a block diagram of a surveillance device according to an embodiment of the present invention, FIG. 2 is a time chart for explaining the operation of the video signal brightness discrimination of the surveillance device, and FIG. 3 is a video signal presence / absence discrimination of the surveillance device. It is a time chart explaining operation. 1 ... Television camera, 2 ... Magnetic recording / reproducing device,
5 ... Clamp circuit, 6 ... Comparator, 7 ... Reference voltage setting circuit, 8 ... Hold circuit, 9 ... Detection circuit,
10 ... Output circuit.

Claims (1)

(57) [Claims] 1. A magnetic recording / reproducing apparatus for surveillance which records a video signal outputted from a surveillance imaging device, comprising a clamp circuit for keeping a pedestal level of the video signal at a constant voltage, and a clamp circuit outputted from this clamp circuit. A comparator that compares the video signal voltage with the reference voltage output from the reference voltage setting circuit to determine the brightness of the video signal; and a hold circuit that holds the output signal of this comparator for a certain period of time and outputs the video brightness signal to the notification means. Magnetic recording / reproducing apparatus for monitoring.