JPS60196021A - Calling device using cable shielding layer as transmission line - Google Patents

Abstract

PURPOSE:To improve the efficiency of a maintenance operation job by providing a modulation circuit, a converter and an FM demodulation circuit to a calling device and using an underground calbe shielding layer as a communication transmission line among workers of scattered working sites. CONSTITUTION:A calling device uses a shielding layer 5 for underground cable of an underground power distribution system as a transmission line. Then the sounds given through a mike 6 are modulated to FM signals by an FM modulation circuit 7 at the transmission side. These modulated FM signals are converted into current signals by a converter 8, and the current signals are injected to the layer 5 as a signal current by the converter 8 and transmitted to the receiver side. Then the signal current is received by a current detector 9. The FM of the received signal current is demodulated by an FM demodulation circuit 10 and converted into sounds. These sounds are delivered through a speaker 11. An earth resistance 4' is added. Thus it is desired with this calling system to send the speech every single side as a press talk system owing to the great reduction of power consumption a battery and a simple structure.

Description

[Detailed description of the invention] The present invention relates to a telephone communication device.

When constructing, maintaining, and operating underground power distribution equipment, it is necessary to maintain close communication between the line opening/closing operation point and the construction site in order to ensure safety and ensure proper work processing.

There are two methods of communication: direct communication by a person or the use of radio equipment, etc. However, if the communication point is far away or one side is in a basement, it is difficult to communicate information to the target The problem was that the radio waves did not reach the station, or even if they did arrive, they were too noisy to be audible, so radio relay stations had to be placed in multiple locations, which required a lot of work.

It is an object of the present invention to provide an underground cable shielding layer that eliminates such drawbacks and can be suitably used as a means of communication between workers when carrying out construction work in an underground power distribution system, especially when the work site is spread out. The purpose is to improve the efficiency of maintenance and operation work for underground power distribution systems, especially when construction work is being carried out in tunnels or valleys between buildings where underground cables are installed in underground power distribution systems, and radio waves cannot be received by communication radios. It is an object of the present invention to provide a telephone communication device using an underground cable shielding layer as a transmission path with reduced noise and which can be suitably used in places where there is no noise.

Embodiments of a communication device according to the present invention will be described below based on the drawings.

FIG. 1 shows an example of a power distribution system using cable wiring. A main power line is branched from a feeder of a substation to a plurality of branch power cables 2 via a multi-circuit switch 1, and introduced into a cabinet 3. The cabinet 3 has a π-shaped branch, with one end distributed to the customer and the other end distributed to other cabinets 3.

On the other hand, the shielding layer of the power cable is connected all at once in the multi-circuit switch j and the cabinet throat 3, and is connected to the ground wire 4. A transmitting/receiving device is attached to this ground wire via a current transformer (clamp CT).

FIG. 2 shows an outline of the telephone communication device of the present invention.

As shown in FIG. 2, the communication device of the present invention uses the shielding layer 5 of the underground cable connected to the underground power distribution system as a transmission path, and on the transmitting side, the voice from the micro is converted into FM by the Flv'l conversion circuit 7. The modulated FM signal is converted into a current signal by a converter 8, which injects it into the shielding layer 5 as a signal current, and receives +! 1.11, is received by the current detector 9, and the FM of the received signal current is converted into ii&+yIIL sound by the FM demodulation circuit 10, which is output from the speaker 11. 47 in Figure 2
indicates ground resistance.

Next, details of the telephone communication device of the present invention will be explained with reference to the block diagram shown in FIG.

In the example shown in FIG. 3, it is assumed that two devices having the same configuration are used to make a telephone call, and both are portable devices that use batteries as power sources.

First, to explain a transmission example, the audio signal from the micro is sent to an audio amplification circuit (an automatic level control (ALC) circuit is activated to prevent waveform distortion due to excessive input).
12.

The amplified audio signal is modulated into an FM switching circuit 7IiM signal. I! II.The amplified audio signal is frequency modulated (FM
) tU inputted to circuit 13& and outputted from oscillation circuit 14
Modulate the transmitted wave with an audio signal.

Furthermore, carrier waves must be approved by the Minister of Posts and Telecommunications for telegraphs, telephones, and other communications equipment that conduct high-frequency currents of 10 kllz or less on electrical lines as specified in Article 100, Paragraph 1, Item 1 of the Radio Law. .5 ktlz.

The modulated signal is input to a power amplifier circuit 16 through a low pass filter (1-PF) 15 in order to remove high frequencies. The signal input to the power amplification circuit 16 is amplified and injected into the underground cable shielding layer 5 by a current transformer (CT) 8.

The reason why the voice signal is first modulated into FM by the FM modulation circuit 7 as described above, and then the FM signal is injected as a signal current into the shielding layer by CT to perform a telephone call is as follows.

When audio is input to the micro, the 3kllz band pass filter will filter out sounds below 30011z and 3kllz (30
00117,) - cuts the audio in the band of approximately 30
0~3000+17. If the voice signal is amplified and injected into the underground cable shielding layer as a signal current to make the call, the underground cable shielding layer While the signal current is passing through, harmonics of the commercial frequency 5011z near the audio band may be included in the signal current. When the receiving side receives a signal current that contains such harmonics, the harmonic components are output as noise, which may make it impossible to make a call.7 To counter this noise, it is necessary to first turn off the voice as described above. A preferred method is to perform FM modulation and inject the FM modulated signal as a signal current into the underground cable shielding layer from the CT to make a call. This allows transmission and reception to be performed without being affected by harmonics near the voice band.

Next, the receiving side will be explained.

Since the signal received by the current detector (CT) 9 from the underground cable shield layer 5 is at a low level, a signal amplification circuit (LC circuit is turned on to prevent waveform distortion due to excessive input) is installed.

) 17 and amplified.

The amplified signal is passed through a band pass filter (BPF) 1B to remove noise such as harmonics, and the negative signal is input to the FM demodulation circuit l, and the other signal is input to the muting circuit 19.

The signal input to the FM demodulation circuit 10 is demodulated into an audio signal and amplified to an appropriate level by the signal amplification circuit 20.

Since the audio signal amplified by the signal amplification circuit 20 contains a carrier component, it is removed through the LPF 21.

The signal passed through the LPF 21 is input to the power amplifier circuit 23 through the analog switch 22.

The signal input to the power amplification circuit 23 is amplified and output from the speaker II.

Furthermore, when there is no modulation signal on the receiving side, the signal input to the muting circuit 19 is outputted as an analog switch ON/OFF signal by the muting circuit 19 in order to prevent unnecessary sound from the speaker due to noise. .

The above communication method is preferably a breath talk method, which has the advantage of significantly reducing battery consumption and the simplicity of the device, and allows one side to speak to each other.

According to the communication device of the present invention, it can be suitably used as a means of communication between workers when carrying out construction work in an underground power distribution system, especially when the work site is spread over a wide area. , it is possible to improve the efficiency of operational tasks.

The telephone communication device of the present invention has no noise and can freely communicate even in areas where radio waves cannot reach with a wireless device.

The above-mentioned grounding resistor 4 in the present invention differs depending on the grounding situation, but since it provides a signal with a current, it is possible to obtain a signal with a value that is independent of the grounding situation, and it can be confirmed that it can be sufficiently reproduced by the receiving amplification system for practical use. did it. Furthermore, by using C and T, it is possible to provide a low-cost device that does not require a modulator or detector, and communication is possible by simply inserting a clamp CT into the ground wire (wire color green) installed in the power equipment. The result is something that anyone can use easily and that can communicate even when the line is live.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing an example of a power distribution system using cable wiring, FIG. 2 is a system diagram showing an embodiment of the communication device of the present invention, and FIG. 3 is an example of a block diagram of the communication device of the present invention. 5---m----Underground cable shielding layer 6------
- Microphone 7, ----- FM modulation circuit 8 --- Converter (C'r) 9 --- Current detection (CT) IQ --- FM demodulation circuit] 1- −−−−−−−Speaker patent applicant Toko Electric Co., Ltd. (Patent attorney Yoshihiro Sato Figure 1)

Claims (1)

[Claims] A modulation circuit that FM modulates an audio signal, a converter that converts the modulated FM signal into a current signal and injects it into the shielding layer of the power cable, and an FM recovery circuit that links the signal received from the converter to the audio signal. A communication device that uses a power cable shielding layer as a transmission path, comprising: