JPS6217919Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an alarm device that uses a common television line to share alarm signals in multiple subscriber homes, and particularly to an alarm device that can detect disconnection.

In general, this type of alarm device transmits a television signal to each subscriber's home 6 via a communal antenna 1, a head end 2, a trunk amplifier 3, a branch amplifier 4, and a tap-off 5, as shown in FIG. It is constructed by connecting an alarm receiving board 7 to any part of the main line system via a signal separator 8. and,
In the shared system alarm device, a specific signal frequency is assigned to each tap-off 5, and the alarm signal is shared among a plurality of subscriber homes. Therefore, it is necessary to be able to issue an alarm signal from any of the subscriber's homes that share the alarm signal.

As this shared system alarm device, a power supply circuit is provided in either the branch amplifier 4, the main amplifier 5, or the alarm receiving board 7, and this power supply is used to generate alarm indicators, alarm signal generators, etc. installed in the subscriber's home. A driving mechanism has been proposed. FIG. 2 is a block diagram showing the portion distal to the tap-off of this alarm system.

In the figure, the tap-off 5 includes a branching/distributing circuit 9 for branching and distributing television signals, and a television signal passing filter 10 connected to the input/output end and the branching end of the branching/distributing circuit 9. A low-pass filter 11 connected between the input and output terminals 5a and 5b and between each branch terminal 5c and 5c, and the input terminal 5a.
(or output terminal 5b) and branch terminal 5c, a voltage drop setting resistor 12 is provided. The television signal separator 13 is installed in each subscriber's house 6, one end is connected to the branch terminal 5c via the protector 14, and the television receiver 22 is connected to one of the other branched ends.
On the other hand, an alarm line 17 is connected in series with an alarm indicator 16 such as a buzzer and an indicator light, and an alarm switch 15.
are connected via a power supply current passing filter 18. Further, in the line connecting the input terminal 5a of the tap-off 5 to the alarm display 16, there is a voltage drop detection circuit 19 for detecting a voltage drop due to alarm, and an alarm signal generator 20 controlled by the detection circuit 19. and.

Note that the alarm display 16 is connected to the alarm switch 1.
It is sufficient to operate in conjunction with 5 on and off, so
It can also be driven by the commercial power supply at each subscriber's home. In this case, the alarm display 16 is connected to the alarm line 17.
It is not necessary to connect to.

The alarm signal is constantly transmitted at a specific frequency from the alarm signal generator 21 in order to facilitate the discovery of wire breakage accidents, and is sent from the tap-off 5 to the alarm reception board 7 via the television public listening line. Then, in case of an emergency, if one of the homes turns on the alarm switch 15,
The alarm indicator 16 connected to or interlocked with this operates, and a voltage drop occurs in the voltage drop setting resistor 12, which is detected by the voltage drop detection circuit 19, and its output is used as the alarm signal generator 20. is turned off, the alarm signal is interrupted, and an emergency condition is detected.

This type of alarm device needs to be able to easily detect line breakage, and the alarm signal line connecting the alarm receiving board 7 and the alarm signal generator 20 can be monitored by the above-mentioned constant transmission method. However, disconnections in lines other than those described above cannot be detected by this method. Therefore, as shown in Figure 2,
It is considered that a termination resistor 23 is connected in parallel to the alarm switch 15 so that a weak current flows even when the alarm switch 15 is off, and a voltage drop caused by this current is detected to detect a disconnection. .

In this case, since the tap-off normally has four branch terminals, four terminating resistors 23 are connected in parallel as shown in FIG. In the figure, the input voltage of the voltage drop setting resistor 12 is V ₀ , and the resistance values of the voltage drop setting resistor 12 and the terminating resistor 23 are
Assuming R ₀ and R ₁ , the voltage Vn across the termination resistor 23 during normal operation is as follows.

Alternatively, if one of the lines including the terminating resistor 23 is disconnected, the voltage V ₁ will be as follows.

Therefore, the voltage change ratio between the normal state and the disconnected state is V ₁ /Vn=4R ₀ +R ₁ /3R ₀ +R ₁ (3).

This voltage change ratio needs to be 3 dB or more when detecting a disconnection, taking into consideration fluctuations in power supply voltage, influence of line resistance, and temperature characteristics of the detection circuit. However, as is clear from equation (3), the above proposal cannot be realized because a change ratio of 3 dB cannot be obtained regardless of the values of R ₀ and R ₁ .

The present invention was made to solve this problem.The subscriber premises for each tap-off are divided into two groups, and diodes are connected in series with a terminating resistor in the forward and reverse directions for each group. The power supply current flowing through the terminating resistor is separated into two systems, positive and negative, for each group, and the voltage change ratio between normal and disconnection is 3 dB or more, making it possible to detect line disconnections. The purpose is to provide a warning device that uses railroad tracks.

The present invention will be described below based on embodiments shown in the drawings.

FIG. 4 is a block diagram showing a portion distal to the tap-off of an embodiment of the present invention, and FIG. 5 is a circuit diagram showing the connection relationship of the main parts of this embodiment. In these figures, the alarm device of the present invention is a shared type alarm device in which a driving power supply circuit is provided in the branch amplifier 4 etc.
are divided into two groups, and the alarm switch 15 at each subscriber's home 6 is activated.
A terminating resistor 23 is connected in parallel to the terminating resistor 23, and a diode 24 is connected in series with the terminating resistor 23 to the signal line 17.
are inserted and connected in the forward direction in one group and in the reverse direction in the other group, and the diode 2 is connected from the input terminal 5a or output terminal 5b of the tap-off 5.
Voltage drop detection circuits 25 and 26 are installed in the line connecting 4.
, alarm signal generator 20 , and disconnection signal generator 27
It has been established that

The alarm switch 15 is composed of a push button switch, a sensor, etc., and is closed in an emergency, and is connected to the power supply circuit 4a provided in the branch amplifier 4 etc. as shown in FIG.
A closed circuit is formed between the voltage drop setting resistor 12 (for example, AC 30V) and the ground, and the power supply current causes a voltage drop in the voltage drop setting resistor 12, and the alarm indicator 16 is activated.

The terminating resistor 23 is connected in parallel with the alarm switch 15, and is used to cause a weak current to flow when the switch 15 is opened. The smaller the resistance value R ₁ is, the greater the voltage change ratio in the event of a disconnection, but since the change in voltage drop during an emergency will be smaller and the power consumption will be larger, it is usually the same value as R ₀ . do. Note that when six terminating resistors are connected in parallel, R ₁ must be set to a smaller value than R ₀ from the above equation (3).

The diode 24 is
Alarm line 1 for subscriber houses 6 divided into two groups each house
7 in series with the terminating resistor 23 in the forward direction in one group and in the reverse direction in the other group, and separates the power supply current flowing through each terminating resistor 23 into positive and negative half waves for each group. The insertion position may be any position on the alarm line 17 from the power supply current passing filter 18 to the ground point as long as it is connected in series with the terminating resistor 23. However, in order not to interfere with the detection of voltage drops of opposite polarity, the voltage drop detection circuit 25, which will be described later,
It is necessary to set it on the ground side from the connection point of 26.

The voltage drop detection circuits 25 and 26 are connected to the alarm line 17 via a power supply current passing filter 18 via forward and reverse diodes 24, respectively, at an arbitrarily selected subscriber's premises 6a. Both have upper and lower threshold values, detect a voltage drop in the voltage drop setting resistor 12 in an emergency using the lower threshold value, and output a control signal to control the alarm signal generator 20. Further, a voltage increase due to a disconnection of a line other than the alarm signal line is detected using an upper threshold value, and a control signal for controlling the disconnection signal generator 27 is output. Note that since both have the same function except that they are driven by positive and negative half-waves of the power supply current, they can be combined into one by using a rectifier circuit such as a diode bridge.

The alarm signal generator 20 is connected to the television signal separator 13 via an alarm signal passing filter 21,
Usually, it oscillates at a specific frequency assigned in advance, and always sends an alarm signal to the alarm signal line. In an emergency, the switches 20a and 20b are turned off by the control signals output from the voltage drop detection circuits 25 and 26 to stop oscillation or transmission, and the alarm receiving board 7 detects this as an alarm signal and displays it. do. Note that although the above is a constant transmission system, it is of course possible to configure the alarm signal to be transmitted only in an emergency. This alarm signal generator 20 is driven by the power supply current from the power supply circuit 4a of the branch amplifier 4, together with a disconnection signal generator 27 to be described later.

The disconnection signal generator 27 is connected to the alarm signal line via the alarm signal passing filter 21 in the same manner as described above, and oscillates at a frequency different from that of the alarm signal generator 20 to distinguish it from the alarm signal, and always outputs the disconnection signal. is being sent. In the event of a disconnection, depending on whether the diode 24 connected to the disconnected line is in the forward or reverse direction, a control signal output from the voltage drop detection circuit 25 or 26 connected to the diode 24 in the same direction causes the switch 27a to be switched on. or 27
b is turned off, oscillation or transmission is stopped, and the alarm receiving board 7 detects this as a disconnection signal and displays it.

In the above embodiment, the voltage drop detection circuits 25, 2
6. Alarm signal generator 20 and disconnection signal generator 27
is installed at an arbitrary subscriber's home 6a, but the present invention is not limited to this. That is, if the voltage drop detection circuits 25 and 26 can detect voltage changes for both positive and negative systems, the voltage drop setting resistor 1
The terminal resistor 2 may be provided anywhere on the line connecting the terminal resistor 2 and the terminal resistor 23. Further, if the alarm signal generator 20 and the disconnection signal generator 27 can send these alarm signals from the tap-off 5 to the television common listening line, the alarm signal generator 20 and the disconnection signal generator 27 will send the alarm line 17 from the input terminal 5a or output terminal 5b of the tap-off 5. It can be installed anywhere on the connecting line. For example, they can also be provided within the tap-off 5.

As explained above, the present invention divides the subscriber premises for each tap-off into two groups and separates the power supply current flowing through the terminating resistor into two systems, positive and negative, for each group by configuring as described above. , the number of terminating resistors connected to the voltage drop setting resistor can be effectively halved, reducing the ratio of voltage change between normal and disconnected conditions.
3 dB or more, and has the effect of realizing disconnection detection of lines other than alarm signal lines, which has been difficult in the past.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing an example of an alarm device that uses a TV common listening line, Figure 2 is a block diagram showing the terminal end of the tap-off of a shared alarm system, and Figure 3 is a voltage drop setting resistor and terminal. A circuit diagram showing the relationship with the resistor, FIG. 4 is a block diagram showing the end portion from the tap-off of an embodiment of the alarm device of the present invention, and FIG. 5 is a circuit diagram showing the connection relationship of the main parts of the above embodiment. It is a diagram. 4...branch amplifier, 5...tap-off, 6...
Subscriber's home, 12... Resistor for voltage drop setting, 13...
...TV signal separator, 15...Alarm switch, 1
6... Alarm indicator, 17... Alarm line, 20...
Alarm signal generator, 23... Termination resistor, 24... Diode, 19, 25, 26... Voltage drop detection circuit, 27... Disconnection signal generator.

Claims (1)

[Scope of utility model registration request] A power supply circuit for driving an alarm signal generator, etc. is installed in either the branch amplifier, main amplifier, or alarm reception board connected to the television common listening line, and each tap-off is
A low-pass filter is provided between the input/output terminals and each branch terminal to bypass the alarm signal and the power supply current supplied from the power supply circuit, and a voltage drop setting resistor is provided between the input or output terminal and the branch terminal. In a shared system alarm system in which a television signal separator is installed in a subscriber's home and a warning line equipped with a warning switch is connected to the television signal separator, a terminating resistor is connected in parallel to the warning switch. At the same time, the subscriber premises for each tap-off are divided into two groups, and a diode is inserted and connected in series with a terminating resistor in one group in the forward direction and in the other group in the reverse direction, and the above-mentioned A pair of voltage drop detection circuits are connected through diodes in different directions in the line connecting the input or output terminal of the tap-off to the above-mentioned terminating resistor, and are controlled by a pair of voltage drop detection circuits, each having an upper and lower threshold, and the above-mentioned voltage drop detection circuit. What is claimed is: 1. An alarm device using a television common listening line, characterized in that an alarm signal generator and a disconnection signal generator are provided, each of which oscillates at a different frequency.