JPH09154035A - Level detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To judge the propriety of the strength of television signals at a television outlet by detecting only a required frequency band in input signals, comparing smoothed DC voltage signals with a reference value and performing display. SOLUTION: High frequency signals inputted from an input terminal T1 are branched and only the signals of the same frequency band as the frequency band of the television signals are passed through in a band-pass filter 61, detected in a detection diode 62 and turned to a pulsating current for which the negative voltage side of the signals of a carrier frequency is cut. The pulsating current is flattened in a smoothing circuit composed of a capacitor 63 and a high frequency choke coil 64, an obtained DC voltage is compared with a reference voltage in comparator circuits 69 and 70 and the strength of the television signals at the television outlet is displayed by display circuits 74-76. Thus, when this level detector is connected to the television outlet, without viewing a television screen, whether or not the level of the television signals at the part of the television outlet is appropriate is judged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television co-listening system in which television broadcast radio waves received by an antenna are transmitted to a television receiver via a television co-listening wiring and a television outlet. The present invention relates to a level detector that detects the strength of a signal.

[0002]

2. Description of the Related Art Generally, in a television co-listening wiring system, when receiving a television broadcast radio wave, the television broadcast radio wave received by an antenna 1 is distributed to each room by a distributor 4 as shown in FIG. It is adapted to be transmitted to the television receiver 2 via the television outlet 5 installed in the. However, the signal received by the antenna 1 is already weakened at the place where the TV outlet 5 is installed due to the loss of the cable to be wired, the distribution loss of the distributor 4, and the loss of the distributor 4 itself. In some cases, it becomes difficult to receive the image in 2.

In order to prevent this, the booster 3 is installed at a position as close as possible to the antenna 1, and the booster 3 is constructed so as to compensate for the distribution by the distributor 4 and the loss due to the cable. The magnitude of the input signal to the booster 3 includes the distance from an antenna (not shown) for transmitting television broadcast waves, the transmission power, the gain of the receiving antenna 1 and the input terminal of the booster 3 from the receiving antenna 1. Determined by the length of the cable up to. Further, the gain of the booster 3 depends on the number of distributions, the length of the cable to the TV outlet 5, the form of the TV outlet 5, and depends on the co-listening wiring. Normal,
In the TV receiver 2, about 60-80 dBμ in the VHF band,
A signal strength of about 70 to 85 dBμ is required in the UHF band. The strength of the signal received by the receiving antenna 1 is not always the optimum reception level of the television receiver 2, and the strength of the signal greatly changes due to the co-listening wiring. For this reason, the booster 3 is generally provided with a level adjusting function, but whether or not the signal strength at the TV outlet 5 is at an optimum level is determined by the TV outlet 5 when adjusting. The judgment was made by looking at the image receiving screen of the connected TV receiver 2.

[0004]

However, in general, the booster 3 is often installed on the attic, on the roof, or on the wall surface, and is often separated from the TV outlet 5.
Therefore, in such a case, one person looks at the image receiving screen of the television receiver 2 connected to the television outlet 5 and the other person performs the level adjustment of the booster 3 or the two persons work first, or After making an approximate level adjustment to
It was necessary to repeat the work of going to the screen of the television receiver 2 and readjusting the level several times. In this case, you can work alone, but booster 3
If it was installed at a high position, you would have to climb and descend many times, which was a safety issue.

Further, when the television receiver 2 is not connected to all the installed television outlets 5,
When trying to confirm that all TV outlets 5 can receive images, there is a problem in that the user must walk with the television receiver 2.

The present invention has been made in view of the above points, and it is an object of the present invention that the strength of a television signal at a television outlet is appropriate without looking at the screen of the television receiver. It is to provide a level detector which can determine whether or not.

[0007]

According to the first aspect of the present invention,
A level detector for detecting the strength of a television signal at the television outlet of a television co-listening system in which television broadcast radio waves received by an antenna are transmitted to a television receiver through a television co-listening wiring and a television outlet. A bandpass filter that passes only a necessary frequency band among the input signals, a detection unit that detects the output signal of the bandpass filter, a smoothing unit that smoothes the output signal of the detection unit, A comparison unit that compares the DC voltage signal output from the smoothing unit with a preset reference value, and a display that indicates the strength of the TV signal at the TV outlet based on the comparison result of the comparison unit. It is characterized by comprising a section.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a schematic configuration of a level detector showing an example of an embodiment of the present invention. The level detector according to the present embodiment includes the band pass filter 6
1, a smoothing circuit including a detection diode 62, a capacitor 63 and a high frequency choke coil 64, and comparison circuits 69 and 7
0, inversion circuits 71 and 72, AND circuit 73, display circuit 7
4 to 76. The band pass filter 61 passes only a signal in the television band from the high frequency signal input from the input terminal TI, and is, for example, 90 MHz to.
Pass the 270 MHz signal. Detection diode 62
Detects the television signal that has passed through the band-pass filter 61 and generates a pulsating flow. When the intensity of the high frequency signal input from the input terminal TI is weak, the band pass filter 6
The television signal that has passed through 1 may be input to the detection diode 62 after being amplified to a required level by an amplifier (not shown). The smoothing circuit including the capacitor 63 and the high frequency choke coil 64 smoothes the pulsating current signal output from the detection diode 62. The DC signal obtained as the output of this smoothing circuit indicates the strength of the television signal. Each of the comparison circuits 69 and 70 is composed of a comparator. The comparison circuit 69 is for detecting a level under, a television signal is input to the-side terminal, and a reference formed by the resistors 65 and 66 to the + side terminal. The voltage is input. That is, the comparison circuit 69 responds with a signal strength lower than the reference voltage. The comparison circuit 70 is for detecting level over, the television signal is input to the + side terminal, and the reference voltage formed by the resistors 67 and 68 is input to the − side terminal. That is, the comparison circuit 70 responds with a signal strength higher than the reference voltage. The AND circuit 73 is a comparison circuit 69, 70.
The logical product of the inversion signal of the output signal of This inversion signal is generated by the inversion circuits 71 and 72. The display circuit 74 is composed of an LED, and captures and displays the output of the comparison circuit 69. The display circuit 76 is composed of an LED and captures and displays the output of the comparison circuit 70. That is, the display circuit 74 displays when the strength of the television signal is lower than the threshold value, and the display circuit 76 displays when the strength of the television signal exceeds the threshold value. Further, the display circuit 75 is also composed of an LED, and takes in the output of the AND circuit 73 and displays it. That is,
The display circuit 75 is for displaying when the strength of the television signal is the optimum signal strength. Incidentally, 77 to 79 are diodes, and 80 to 82 are resistors.

Next, the operation of the level detector according to this embodiment will be described. The high frequency signal input from the input terminal TI is branched, one signal is sent to the output terminal TO, and the other signal is input to the band pass filter 61. In the band pass filter 61, only the signal in the frequency band similar to the frequency band of the television signal is passed and detected by the detection diode 62, resulting in a pulsating flow in which the negative voltage side of the carrier frequency signal is cut. This pulsating flow is flattened by a smoothing circuit to obtain a DC voltage. In the smoothing circuit, the high frequency component is averaged by charging / discharging the capacitor 63, the high frequency component is cut off, and the DC voltage is finally obtained. This DC voltage becomes the strength of the television signal. A larger direct current voltage can be obtained when the capacitance of the capacitor 63 and the inductance of the high frequency choke coil 64 are larger. The output of the smoothing circuit indicating the strength of the television signal (television signal strength) is compared with the reference voltage in the comparison circuits 69 and 70. A display indicating that the signal strength is insufficient (lower than the level required by the television receiver 2) is displayed. When the voltage is higher than the reference voltage for level over, the comparison circuit 70 outputs the signal and the display circuit 76 displays that the strength of the television signal is too high. When the strength of the TV signal is higher than the reference voltage of the level under and lower than the reference voltage of the level over, the display circuit 75 is displayed so that the strength of the TV signal is known to be the optimum level. .

Therefore, if the level indicator of this embodiment is connected to the TV outlet 5, the level of the TV signal in the TV outlet 5 portion without connecting the TV receiver 2 to the TV outlet 5 and watching the TV screen. It is possible to judge whether or not is appropriate.

[0011]

As described above, according to the first aspect of the present invention, a television receiver configured to transmit television broadcast radio waves received by the antenna to the television receiver via the television common listening wiring and the television outlet. A level detector that detects the strength of the TV signal at the TV outlet of the listening system, and detects the output signal of the bandpass filter and the bandpass filter that passes only the necessary frequency band of the input signal. A detection unit, a smoothing unit that smoothes the output signal of the detection unit, a comparison unit that compares the DC voltage signal output from the smoothing unit with a preset reference value, and a television based on the comparison result of the comparison unit. Since the display section is provided to display the strength of the TV signal at the outlet, the strength of the TV signal at the TV outlet can be displayed without looking at the screen of the TV receiver. It is could be provided level detector reveals whether or not appropriate.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a schematic configuration of a level indicator according to an example of an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing a television common listening wiring system.

[Explanation of symbols]

 1 Antenna 2 Television Receiver 3 Booster 4 Distributor 5 Television Outlet 61 Band Pass Filter 62 Detection Diode 63 Capacitor 64 High Frequency Choke Coil 65-68 Resistor 69, 70 Comparison Circuit 71, 72 Inversion Circuit 73 AND Circuit 74-76 Display Circuit 77 ~ 79 diode 80 ~ 82 resistance TI input terminal TO output terminal

Claims (1)

[Claims] 1. The strength of a television signal at the television outlet of a television co-listening system configured to transmit television broadcast radio waves received by an antenna to a television receiver via a television co-listening wiring and a television outlet. A level detector, which is a band-pass filter that passes only a necessary frequency band of an input signal, a detection unit that detects an output signal of the band-pass filter, and a smooth output signal of the detection unit. A smoothing unit, a comparing unit that compares the DC voltage signal output from the smoothing unit with a preset reference value, and the strength of the TV signal at the TV outlet based on the comparison result of the comparing unit. A level detector characterized by comprising a display unit for displaying.