JPS645241Y2 - - Google Patents
Info
- Publication number
- JPS645241Y2 JPS645241Y2 JP1980174247U JP17424780U JPS645241Y2 JP S645241 Y2 JPS645241 Y2 JP S645241Y2 JP 1980174247 U JP1980174247 U JP 1980174247U JP 17424780 U JP17424780 U JP 17424780U JP S645241 Y2 JPS645241 Y2 JP S645241Y2
- Authority
- JP
- Japan
- Prior art keywords
- circuit
- reference voltage
- voltage
- detection
- water intrusion
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000001514 detection method Methods 0.000 claims description 56
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 29
- 239000004020 conductor Substances 0.000 claims description 16
- 230000005856 abnormality Effects 0.000 claims description 12
- 230000000295 complement effect Effects 0.000 claims description 4
- 238000009413 insulation Methods 0.000 description 12
- 238000013459 approach Methods 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 239000012212 insulator Substances 0.000 description 3
- 239000010410 layer Substances 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 239000004698 Polyethylene Substances 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000007654 immersion Methods 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- -1 polyethylene Polymers 0.000 description 2
- 229920000573 polyethylene Polymers 0.000 description 2
- 239000011253 protective coating Substances 0.000 description 2
- 230000035945 sensitivity Effects 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000007257 malfunction Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
Landscapes
- Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
- Examining Or Testing Airtightness (AREA)
Description
【考案の詳細な説明】
本考案は、水または水と油との混合液のような
非絶縁性の液体による浸液・漏液（以下、浸水・
漏水という）を検知するための検出装置に関する
ものである。[Detailed description of the invention] The present invention is designed to prevent liquid immersion/leakage (hereinafter referred to as water immersion/leakage) caused by non-insulating liquids such as water or a mixture of water and oil.
This invention relates to a detection device for detecting water leakage.
地下室、地下道あるいは水分を嫌う物品の貯蔵
庫等における浸水・漏水を早期に検知して、前記
損失を未然に防止することが強く望まれている。 There is a strong desire to prevent such losses by early detection of water intrusion or leakage in basements, underground passages, or storage areas for items that dislike moisture.
従来上記要望に応えるものとして、浸水・漏水
によつて電気的特性の変化する検知線とその検知
線の電気的特性の変化を検出する検出部からなる
装置が提案されている。 Conventionally, in order to meet the above-mentioned demands, a device has been proposed that includes a detection wire whose electrical characteristics change due to water intrusion or water leakage, and a detection section that detects the change in the electrical characteristics of the detection wire.
ところで、検知線の電気特性の変化を検出する
に際し、もしも検知線に断線が生じていた場合に
は、その検知線の断線箇所よりも先端の方で浸
水・漏水による電気特性の変化が生じても、それ
を検知し得ないことになるので、浸水・漏水の検
出とともに検知線の断線をも検知し得る検出装置
が求められている。 By the way, when detecting changes in the electrical characteristics of a detection wire, if there is a break in the detection wire, the change in electrical characteristics due to water intrusion/leakage will occur at the tip of the detection wire rather than the breakage point. Therefore, there is a need for a detection device that can detect not only water intrusion and water leakage but also disconnection of the detection wire.
さらに、従来の検出装置では一般に静電容量法
や特性インピーダンス法によつて検知する方法が
用いられており、そのため高感度のものを得るた
めには高価な装置が必要であつた。 Furthermore, conventional detection devices generally use a capacitance method or a characteristic impedance method, and therefore, an expensive device is required to obtain high sensitivity.
しかも、前記のごとく検知線の断線をも検知し
得るようにするためにはいつそう高価になるの
で、安価にして感度がよくしかも検知線の断線を
も検出し得る検出装置の提供が強く望まれてい
た。 Moreover, as mentioned above, it would be very expensive to be able to detect a disconnection in the detection line, so it is highly desirable to provide a detection device that is inexpensive, has high sensitivity, and is also capable of detecting disconnection in the detection line. It was rare.
本考案は以上の要望に応えるべく鋭意検討を重
ねた結果完成させた浸水・漏水検出装置に関する
もので、その特徴とするところは、少なくとも２
本の電極導体を有する浸水・漏水検知線と、この
検知線の２本の電極導体間の絶縁抵抗に対応した
直流電圧を発生する回路と、その直流電圧が所定
の上下限基準電圧の範囲からはずれた時に信号を
発生して継電器回路を作動させる異常検出回路と
を備えた浸水・漏水検知装置にある。 This invention relates to a water intrusion/water leakage detection device that was completed as a result of intensive studies in response to the above requests.It has at least two characteristics.
A water intrusion/leakage detection line having two electrode conductors, a circuit that generates a DC voltage corresponding to the insulation resistance between the two electrode conductors of this detection line, and a circuit that generates a DC voltage that is within a predetermined upper and lower limit reference voltage range. The water intrusion/leakage detection device is equipped with an abnormality detection circuit that generates a signal to activate a relay circuit when disconnected.
次に本考案の一実施例を図面にもとづいて説明
する。 Next, an embodiment of the present invention will be described based on the drawings.
第１図は本考案の一実施例のブロツク線図であ
る。 FIG. 1 is a block diagram of an embodiment of the present invention.
１は検知線、R1は検知線の始端S1，S2からみ
た正常時における抵抗を適当な値に調整するため
の終端抵抗、２は交流電源で、抵抗R2を介して
検知線の始端S1，S2に接続されている。 1 is a detection wire, R 1 is a terminating resistor for adjusting the resistance at normal times as seen from the starting ends S 1 and S 2 of the detection wire to an appropriate value, and 2 is an AC power supply that connects the detection wire via resistor R 2 . Connected to starting ends S 1 and S 2 .
３は前記の抵抗R2を介して検知線の始端に供
給されている交流電圧を整流する整流回路、４は
異常検出回路で、検出線の始端S1−S2間の交流電
圧に対応する整流回路３の直流出力電圧が所定の
上下限基準電圧の範囲からはずれた時、信号を発
生して継電器回路５を作動させる。異常検出回路
４は対補差動入力形演算増幅器OPと、直流基準
電圧回路、すなわち直流電源回路６とこの回路か
ら供給される直流電圧を抵抗R3，VR，R4によつ
て分圧する抵抗分圧回路とで構成され、上限基準
電圧はR3とVRの接続点P1から演算増幅器OP−
１の非反転入力端子に、下限基準電圧は可変抵抗
VRの接点P2から演算増幅器OP−２の反転入力
端子に、それぞれ接続される。 3 is a rectifier circuit that rectifies the AC voltage supplied to the starting end of the detection line via the resistor R 2 , and 4 is an abnormality detection circuit, which corresponds to the AC voltage between the starting ends S 1 and S 2 of the detection line. When the DC output voltage of the rectifier circuit 3 deviates from the range of predetermined upper and lower reference voltage limits, a signal is generated to activate the relay circuit 5. The abnormality detection circuit 4 includes a complementary differential input type operational amplifier OP, a DC reference voltage circuit, that is, a DC power supply circuit 6, and a resistor that divides the DC voltage supplied from this circuit by resistors R 3 , VR, and R 4 . It consists of a voltage divider circuit, and the upper limit reference voltage is connected from the connection point P1 of R3 and VR to the operational amplifier OP−
The lower limit reference voltage is connected to the non-inverting input terminal of 1 by a variable resistor.
The contact P2 of VR is connected to the inverting input terminal of operational amplifier OP-2, respectively.
また、演算増幅器OP−２の負電源端子および、
演算増幅器OP−１の正電源端子はそれぞれ直流
電源の負極および正極に接続される。 In addition, the negative power supply terminal of the operational amplifier OP-2 and
The positive power supply terminal of the operational amplifier OP-1 is connected to the negative pole and the positive pole of the DC power supply, respectively.
さらに、整流回路３の出力端子の正極側は演算
増幅器OP−１の反転入力端子および演算増幅器
OP−２の非反転入力端子に接続される。 Furthermore, the positive side of the output terminal of the rectifier circuit 3 is the inverting input terminal of the operational amplifier OP-1 and the operational amplifier
Connected to the non-inverting input terminal of OP-2.
継電器回路５は、演算増幅器OP−１の出力端
子に接続された増幅器Ａ−１およびリレーRL−
１と、演算増幅器OP−２の出力端子に接続され
た増幅器Ａ−２およびリレーRL−２とから成る。 The relay circuit 5 includes an amplifier A-1 and a relay RL- connected to the output terminal of the operational amplifier OP-1.
1, an amplifier A-2 and a relay RL-2 connected to the output terminal of the operational amplifier OP-2.
また、検知線１は、第２図に示すごとく、可撓
導体１１および１２に、それぞれポリエチレン糸
から成る編組絶縁２１および２２を施した後より
合わせ、その上にテトロン糸から成る保護編組３
０を施したものである。 In addition, as shown in FIG. 2, the detection wire 1 is constructed by applying braided insulation 21 and 22 made of polyethylene thread to the flexible conductors 11 and 12, respectively, and then twisting them together.
0 has been applied.
次に、以上に述べた本考案装置の作動について
説明する。 Next, the operation of the device of the present invention described above will be explained.
検知線１は絶縁体層も保護被覆層も透水可能に
形成されているので、水等の非絶縁性液体が浸入
すると２本の導体間の絶縁抵抗は容易に低下す
る。 Since both the insulator layer and the protective coating layer of the detection wire 1 are formed to be permeable to water, the insulation resistance between the two conductors easily decreases when a non-insulating liquid such as water enters.
一方、絶縁体層はポリエチレン糸によつて、編
組密度が50％以上でかつ厚さが0.3〜0.6mmになる
ように形成されているので、相対湿度の高い環境
下にあつても、吸水性が小さく、かつ適度の編組
密度と厚さを有するので、絶縁抵抗が過度に低下
することはない。 On the other hand, the insulator layer is made of polyethylene yarn with a braid density of 50% or more and a thickness of 0.3 to 0.6 mm, so it has excellent water absorption properties even in environments with high relative humidity. is small and has appropriate braid density and thickness, so insulation resistance does not decrease excessively.
次に、交流電源２の出力電圧をVOボルト、２
導体間の絶縁抵抗をRXオームとすると、端子S1，
S2間に現われる電圧VXは
VX＝VO×R1・Rx／R1＋Rx／R1・Rx／R1＋Rx＋R2
＝VO×R1・RX／R1・RX＋R2（R1＋RX） (1)
となる。今、VO＝12ボルト、R1＝5KΩ、R2＝
10KΩとし、検知線の電極線間の絶縁抵抗RXが
100KΩであつたとすると、(1)式よりVX＝3.87ボ
ルトとなることがわかる。そこで、検知線が浸水
し、絶縁抵抗RXが5KΩまで低下したものとする
と、VX＝2.4ボルトとなる。 Next, set the output voltage of AC power supply 2 to V O volts, 2
If the insulation resistance between the conductors is R x ohm, then the terminals S 1 ,
The voltage V X that appears between S 2 is V (R 1 +R X ) (1). Now, V O = 12 volts, R 1 = 5KΩ, R 2 =
The insulation resistance R X between the electrode wires of the detection wire is 10KΩ.
Assuming that it is 100KΩ, it can be seen from equation (1) that V X =3.87 volts. Therefore, assuming that the detection wire is submerged in water and the insulation resistance R X drops to 5KΩ, V X =2.4 volts.
また、検知線の導体が断線した場合について考
えるに、検知線の導体１１，１２のいずれかまた
は両方に断線が生じたものとし、始端S1，S2から
検知線の方を見た時の絶縁抵抗RX′とすれば
VX＝VO×RX′／R2＋RX′ (2)
となる。RX′は断線箇所が終端に近い時はRXにほ
ぼ等しく、始端に近づくにつれて無限大に近づ
く。 Also, considering the case where the conductor of the detection line is disconnected, assume that either or both of the conductors 11 and 12 of the detection line is disconnected, and when looking at the detection line from the starting ends S 1 and S 2 . If the insulation resistance is R X ′, then V X =V O ×R X ′/R 2 +R X ′ (2). R X ′ is approximately equal to R X when the disconnection point is near the end, and approaches infinity as it approaches the start end.
今、終端の近くで断線が生じ、RX′＝100KΩで
あつたとすると(2)式よりVX＝10.9ボルトとなる。
また、断線箇所が始端に近づくほどVxは12ボル
トに近づく。以上により、VX≦2.4ボルトまたは
VX≧10.9ボルトの時、異常検出回路４が働らき、
継電器回路５を作動させるようにしておけば良い
ことがわかる。 Now, if a disconnection occurs near the termination and R X ' = 100KΩ, then from equation (2), V X = 10.9 volts.
Also, the closer the disconnection point is to the starting point, the closer V x approaches 12 volts. From the above, V X ≦2.4 volts or
When V X ≧10.9 volts, the abnormality detection circuit 4 operates,
It can be seen that it is sufficient to operate the relay circuit 5.
一方、直流電源回路６の出力電圧をVDCとする
と、異常検出回路の上限基準入力電圧Vuは
Vu＝VDC×R4＋VR／R3＋VR＋R4 (3)
となり、下限基準入力電圧VLはP2点の位置によ
つて
VL＝VDC×R4／R3＋VR＋R4 (4)
から
VL＝Vu (5)
の範囲内で変化する。 On the other hand, if the output voltage of the DC power supply circuit 6 is V DC , the upper limit reference input voltage V u of the abnormality detection circuit is V u = V DC × R 4 + VR / R 3 + VR + R 4 (3), and the lower limit reference input voltage V L varies depending on the position of the two points P within the range from V L = V DC × R 4 /R 3 + VR + R 4 (4) to V L = V u (5).
そこで、簡単のため整流回路３の出力直流電圧
が入力交流電圧VXの実効値に等しいものとする
と、Vu＝10.9ボルト、VL＝2.4ボルトとなるよう
に(3)〜(5)式より抵抗値を設定すればよいことにな
る。ただし、検知線が浸水した時に達する絶縁抵
抗は検知線の種類によつて必らずしも5KΩとば
かりは限らないから、VLを２〜６ボルトの範囲
で調節可能にするものとする。また、Vuは必ら
ずしも10.9ボルト以上である必要はなく、できれ
ばやや低い目に設定しておく方が当然安全側にな
る。もつとも、検知線の導体間絶縁抵抗RXが正
常な値である時、断線も生じていないのに誤動作
するようでは困る。前記したようにRX＝100KΩ
の時にVX＝3.87ボルトであつたから、この値よ
りはかなり大きくしておく必要があるので仮に
Vu＝６ボルトとする。 Therefore, for simplicity, if we assume that the output DC voltage of the rectifier circuit 3 is equal to the effective value of the input AC voltage V This means that it would be better to set a higher resistance value. However, since the insulation resistance reached when the detection wire is submerged in water is not necessarily 5KΩ depending on the type of detection wire, VL should be adjustable within the range of 2 to 6 volts. Also, V u does not necessarily have to be 10.9 volts or higher, and it is naturally safer to set it a little lower if possible. However, when the insulation resistance R X between the conductors of the detection wire is at a normal value, it would be a problem if a malfunction occurs even though there is no disconnection. As mentioned above, R X = 100KΩ
Since V X = 3.87 volts at the time of
Let V u =6 volts.
今、VDC＝12ボルトとし、R3＝6KΩ、R4＝
2KΩ、VR＝4KΩとすれば、(3)式よりVu＝６ボル
ト、また(4)〜(5)式よりVL＝２〜６ボルトとなり
上記の目的を達する。 Now let V DC = 12 volts, R 3 = 6KΩ, R 4 =
If 2KΩ and VR=4KΩ, V u =6 volts from equation (3), and V L =2 to 6 volts from equations (4) to (5), thus achieving the above objective.
上記の回路素子の定格値は必要とする検出レベ
ルに応じて当業者であればいかようにも設計し得
るものであり、検知線の終端抵抗R1も電極導体
間絶縁抵抗の正常値が低い場合には必らずしも必
要ではない。 The rated values of the above circuit elements can be designed in any way by those skilled in the art depending on the required detection level, and the termination resistance R 1 of the detection wire also has a low normal value of insulation resistance between electrode conductors. It is not always necessary in some cases.
また、交流電源２を直流電源におきかえれば整
流回路３は不要であるが、その場合は検知線に直
流電圧が加わり、極性効果によつて電極導体の腐
食を惹起する危険性があるので、電解腐食をおこ
しにくい材質の電極導体を用いることがのぞまし
い。 In addition, if the AC power supply 2 is replaced with a DC power supply, the rectifier circuit 3 is not necessary, but in that case, there is a risk that DC voltage will be applied to the detection wire, causing corrosion of the electrode conductor due to the polarity effect. It is desirable to use an electrode conductor made of a material that does not easily cause electrolytic corrosion.
さらに、異常検出回路４は実施例のごとく対補
差動入力形演算増幅器OPを用いることによつて、
小形でコンパクトに構成し得るがこれに限定され
るものではなく、入力電圧が所定の上下限基準電
圧の範囲からはずれた時に作動する過不足電圧継
電器を用いて構成しても良い。 Furthermore, the abnormality detection circuit 4 uses a complementary differential input type operational amplifier OP as in the embodiment.
Although it can be constructed small and compact, it is not limited thereto, and may be constructed using an over/under voltage relay that operates when the input voltage deviates from a predetermined upper/lower limit reference voltage range.
本考案は以上のように構成されているので、次
のような効果を有する。 Since the present invention is configured as described above, it has the following effects.
(イ) 異常検出回路への入力電圧が所定の上下限基
準電圧の範囲からはずれた時、異常検出回路が
働いて継電器回路を作動させるようにしたの
で、前記上下限基準電圧値を適切に設定するこ
とにより浸水・漏水を検知し得るだけでなく、
検知線の断線をも検知することができ、断線の
ために浸水・漏水を検知し損うことがない。(b) When the input voltage to the abnormality detection circuit deviates from the range of the predetermined upper and lower reference voltage limits, the abnormality detection circuit operates and operates the relay circuit, so the upper and lower reference voltage limits can be set appropriately. By doing so, you can not only detect water intrusion and leakage, but also
It is also possible to detect disconnections in the detection line, so there is no chance of failing to detect water intrusion or water leakage due to a disconnection.
(ロ) しかも、断線検出のために高価な装置を付加
する必要がなく、浸水・漏水検知線の２本の電
極導体間に接続する終端抵抗と、浸水・漏水に
よる絶縁抵抗の下限基準値以下への低下と共に
上限基準値以上への増加を検出するための検出
回路と継電器を付加するだけで一体の装置で安
価に断線を検出することを可能にしたものであ
る。(b) Moreover, there is no need to add expensive equipment to detect disconnection, and the termination resistance connected between the two electrode conductors of the water intrusion/leakage detection wire and the insulation resistance due to water intrusion/leakage are below the lower limit standard value. By simply adding a detection circuit and a relay to detect an increase above the upper limit reference value as well as a decrease in the limit, it is possible to detect a disconnection at low cost with an integrated device.
第１図は本考案の一実施例のブロツク線図、第
２図は本考案の実施例に用いた検知線の斜視図
で、図中の符号は次のとおりである。
１：検知線、２：交流電源、３：整流回路、
４：異常検出回路、５：継電器回路、６：直流電
源、１１，１２：導体、２１，２２：絶縁体、３
０：保護被覆、OP：対補作動形演算増幅器。
FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a perspective view of detection lines used in the embodiment of the present invention. Reference symbols in the figures are as follows. 1: Detection wire, 2: AC power supply, 3: Rectifier circuit,
4: Abnormality detection circuit, 5: Relay circuit, 6: DC power supply, 11, 12: Conductor, 21, 22: Insulator, 3
0: Protective coating, OP: Complementary operational amplifier.
Claims (1)
水検知線と、その終端において、前記２導体間
に接続した終端抵抗と、始端において、２導体
間に抵抗を介して接続した交流または直流の電
源と、前記電源が交流の場合は整流回路を介
し、直流の場合は整流回路を介せずして、前記
始端に接続した異常検出回路と、前記異常検出
回路の入力が所定の上限基準電圧以上になつた
時および下限基準電圧以下になつた時に、この
回路の出力によつてそれぞれ作動する断線表示
用継電器回路および浸水・漏水表示用継電器回
路とを備えたことを特徴とする浸水・漏水検出
装置。 ２ 異常検出回路が対補差動入力形演算増幅器
と、この演算増幅器に上限基準電圧および下限
基準電圧を供給する直流基準電圧回路とからな
ることを特徴とする実用新案登録請求の範囲第
１項記載の浸水・漏水検出装置。[Claims for Utility Model Registration] 1. A water intrusion/water leakage detection wire having at least two electrode conductors, a terminating resistor connected between the two conductors at its terminal end, and a resistor connected between the two conductors at its starting end. A connected AC or DC power source, an abnormality detection circuit connected to the start end via a rectifier circuit if the power source is AC, or not through a rectifier circuit if it is DC, and an input of the abnormality detection circuit. It is equipped with a relay circuit for indicating disconnection and a relay circuit for indicating water intrusion/leakage, which are activated by the output of this circuit when the voltage exceeds a predetermined upper limit reference voltage and when the voltage falls below a predetermined lower limit reference voltage, respectively. Characteristic water intrusion/leakage detection device. 2. Claim 1 of the utility model registration claim, characterized in that the abnormality detection circuit consists of a complementary differential input type operational amplifier and a DC reference voltage circuit that supplies an upper limit reference voltage and a lower limit reference voltage to the operational amplifier. The water intrusion/leakage detection device described.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1980174247U JPS645241Y2 (en) | 1980-12-03 | 1980-12-03 |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1980174247U JPS645241Y2 (en) | 1980-12-03 | 1980-12-03 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5797265U JPS5797265U (en) | 1982-06-15 |
| JPS645241Y2 true JPS645241Y2 (en) | 1989-02-09 |
Family
ID=29532292
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1980174247U Expired JPS645241Y2 (en) | 1980-12-03 | 1980-12-03 |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS645241Y2 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0629824B2 (en) * | 1988-11-30 | 1994-04-20 | タツタ電線株式会社 | Leak detection device |
| JPH0620122Y2 (en) * | 1988-11-30 | 1994-05-25 | タツタ電線株式会社 | Leak detection device |
| US8928338B2 (en) * | 2010-11-17 | 2015-01-06 | Delphi Technologies, Inc. | Self diagnostics of a particulate matter sensor |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3662367A (en) * | 1971-01-04 | 1972-05-09 | Bell Telephone Labor Inc | Water alarm and fault-locating for air core plastic-insulated telephone cable |
| JPS51104616A (en) * | 1975-03-12 | 1976-09-16 | Japan Gasoline | |
| US4090193A (en) * | 1976-11-24 | 1978-05-16 | The United States Of America As Represented By The Secretary Of The Navy | Frequency multiplexed water leak detection system |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5390934U (en) * | 1976-12-27 | 1978-07-25 | ||
| JPS6245388Y2 (en) * | 1980-11-29 | 1987-12-04 |
-
1980
- 1980-12-03 JP JP1980174247U patent/JPS645241Y2/ja not_active Expired
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3662367A (en) * | 1971-01-04 | 1972-05-09 | Bell Telephone Labor Inc | Water alarm and fault-locating for air core plastic-insulated telephone cable |
| JPS51104616A (en) * | 1975-03-12 | 1976-09-16 | Japan Gasoline | |
| US4090193A (en) * | 1976-11-24 | 1978-05-16 | The United States Of America As Represented By The Secretary Of The Navy | Frequency multiplexed water leak detection system |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5797265U (en) | 1982-06-15 |
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