US3794947A - Line protector for a communication circuit - Google Patents

Line protector for a communication circuit Download PDF

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Publication number
US3794947A
US3794947A US00187018A US3794947DA US3794947A US 3794947 A US3794947 A US 3794947A US 00187018 A US00187018 A US 00187018A US 3794947D A US3794947D A US 3794947DA US 3794947 A US3794947 A US 3794947A
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United States
Prior art keywords
line
circuit
strip
protector
terminals
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Expired - Lifetime
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US00187018A
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English (en)
Inventor
B Baumbach
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Reliable Electric Co
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Reliable Electric Co
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H71/00—Details of the protective switches or relays covered by groups H01H73/00 - H01H83/00
    • H01H71/10—Operating or release mechanisms
    • H01H71/12—Automatic release mechanisms with or without manual release
    • H01H71/14—Electrothermal mechanisms
    • H01H71/20—Electrothermal mechanisms with fusible mass
    • H01H71/205—Electrothermal mechanisms with fusible mass using a ratchet wheel kept against rotation by solder
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T1/00—Details of spark gaps
    • H01T1/14—Means structurally associated with spark gap for protecting it against overload or for disconnecting it in case of failure

Definitions

  • a solder pellet melts causing the cup and slug to engage due to spring pressure and ground the line through a grounding strip.
  • the grounding strip has plastic insulation bonded to a portion thereof and interposed between the line and ground.
  • heat from one of the carbon blocks is transferred through the cup to the metalic strip. This heat may cause the plastic to melt to provide a backup or secondary low resistance path to ground
  • the protector may also have a resettable over current responsive mechanism in the form of a heat coil in the line. When the heat coil breaks, a printed circuit board, on which the heat coil is mounted, is moved by a volute spring. In over voltage and in over current conditions, the volute spring conducts current from the printed circuit board to the slug and cup and to ground.
  • the protector When an over voltage of short duration is applied to either or both of, the incoming lines connected to the protector, the protector provides an arcgap path to ground so that the overvoltage does not reach inside equipment or central office equipment.
  • an over voltage fault is of prolonged duration, or an over current voltage is such that there is arcing across the arc-gap, the current passing through the arcgap generates sufficient heat to melt a fusible solder pellet.
  • the line is connected to ground through a T-bar ground strip which is, in turn, connected to the ground pin of the protector.
  • the module in the protector containing the solder pellet can be removed and replaced to recondition the protector for subsequent normal operation after the over current fault has been corrected.
  • the module proper also contains contact members in the form of a cup and slug, both of metal of high conductivity, and both surrounded by an insulating sleeve to prevent possible arc-over between the adjacent mo ule for the other line.
  • the cup rests on the metalic T-bar ground strip.
  • the T-bar strip has spaced apart strips or layers (one for each module) of insulating plastic interposed between the base of each cup and the remainder of the T-bar.
  • the module also houses carbon blocks that provide the arc-gap.
  • the solder pellet maintains the cup'and slug apart in opposition to the spring pressure tending to urge the cup and slug into engagement when the solder pellet melts.
  • the spring may be an extended part of the terminal'member that electrically connects the two pins of one line.
  • the T-bar strip also provides a secondary low.resistance path for grounding the line when such over current condition exists as to cause a sufficient heating of the carbon block that is in the cup. Under such conditions, heatfrom the carbon block melts the insulating plastic on the T-bar ground strip to provide a direct low resistance path to the ground pin.
  • the T-bar is of a sufticiently yieldable yet highly conductive material that permits the T-bar to distend upon melting of the insulating plastic strip so as to bring the T-bar into engagement with the base of the contact member that is connected to a pin terminal of the line.
  • one form of the present invention further provides against an over current fault in the line by the use of a heat coil assembly.
  • Theheat generated in the coil as a result of excessive current melts a fusible material following which internal switching within the protector takes place to ground the line and also to actuate an alarm.
  • the arrangement provides for a visual indicating means for showing at a glance which line has been affected by the over current condition.
  • Each line of a circuit pair in the protector has a protective circuit board for establishing the internal connections and for performing the aforesaid switching function, and each printed circuit member carries one of the heat coil assemblies that responds to the over current condition.
  • Each heat coil assembly includes a latch or pawl and a cooperating ratchet wheel to effect the switching action.
  • each printed circuit board is moved by a volute spring that is part of the aforesaid module containing the carbon blocks.
  • the volute spring is particularly effective in this invention in that it has a relatively high current-carrying capacity because the volute spring has a greater cross section of material in the same space as a coil spring with comparable operating force and travel.
  • a further object of this invention is to provide a line protector of the type stated which permits ready replacement of various major parts as may be required for in-service maintainance.
  • Another object of this invention is to provide a line protector that provides two identical arrestor assemblies in one housing and yet prevents interaction between the two assemblies under fault conditions.
  • FIG. 1 is a perspective view of a plugin type of line protector constructed in accordance with and embodying the present invention
  • FIG. 2 is a front elevational view, partially broken away in section, and showing the protector in its normal operating condition;
  • FIG. 3 isan enlarged fragmentary portion of FIG. 2 but showing the condition of the protector following an over current fault in both lines;
  • FIG. 4 is a fragmentary sectional view taken approximately along line 4-4 of FIG. 2;
  • FIG. 5 is a front elevational view of the base and contact assembly of the protector of FIGS. l4 and which forms part of the present invention
  • FIG. 6 is a fragmentary sectional view taken along line 6-6 of FIG. 5;
  • FIG. 7 is a perspective view of the T-bar ground contact strip which forms part of the present invention.
  • FIG. 12 is a sectional view taken approximately along line 1212 of FIG. 11 and showing the condition of the protector when one of the lines is subject to an over current condition that actuates the heat coil therein.
  • DETAILED DESCRIPTION gated detachable housing 16 of generally rectangular cross section.
  • the base 15 and housing 16 are fabricated of a suitable dielectric material, such as molded plastic.
  • the housing 16 maybe secured to the base 15 by bosses 17 which snap into correspondingly shaped openings in the side walls of the housing 16.
  • the upper end of the housing 16, namely the remote from the base 15, has a neck portion 18 terminating in a flange 19,by which the protector may be gripped for removal from the placement into a receptacle.
  • the neck portion 18 defines an opening 20 for use in connection with components of the protector used in the form of the invention shown in FIGS. 8-12.
  • the particular housing construction shown in connection with the form of the inveniton of FIGS. 1-4, especially as concerned the length of the housing and the opening 20, is illustrated simply to point out that the housings of the two forms of the invention may be of generally similar construction.
  • a series of'conductive plug-in terminal pins identified by the reference numerals 25-31 inclusive.
  • the alarm pin 31 is shown in FIG. 1 but is not used in the form of the invention shown in FIGS. 14. However, alarm pin 31 is used in the form of the invention shown in FIGS. 8-12.
  • the irst line pin 25 and the first central office pin 29 are components in one of the lines through the protector whilethe second line pin 26 and second central office pin 30 are components in the other line through the protector 10.
  • the ground pin 27 (and alarm pin 31 when used as described hereafter) are common to both lines while the polarizing pin 28 is an unconnected or dummy pin that assures proper orientation of the protector unit when it is plugged into its receptacle.
  • pins 25 and 29 are electrically and mechanically connected by contact member 35, which is formed of flat springlike material.
  • contact member 35 which is formed of flat springlike material.
  • the connection between the pins 25, 29 is through a generally channel shaped base portion 37 of the contact member 35, the channel shaped portion 37 receiving an elongated rib 38 on the base and having opposed flanges 39, 41 at which the pins 29, 25 are staked.
  • contact member 42 which is identical to contact member 35, connects the pin 26 with the pin 30.
  • leg 48 is centrally of the strip 45 and depends from one edge thereof. On opposite sides of the leg 48 the strip 45 has spaced insulating strips 52, 52 laminated thereto.
  • the insulating strips 52, 52 may be tapes of a polyethylene terephthalate resin, commonly sold under the trademark Mylar. As willbest be seen in FIGS.:
  • the insulating strips 52, 52 are disposed against the channel shaped portions 37 of the respective contact members 35, and for purposed presently more fully appearing.
  • a removable and replacable module 60 for providing a ground to the ground pin 27 in the event of an over voltage or an over current condition.
  • the modules are identical and each includes contact members in the form of a slug 62 and cup 64, both being of copper or other highly conductive material.
  • the slug 62 and cup 64 are surroundedby an insulating sleeve 66.
  • Within the cup 64 is a carbon arc-gap assembly comprising carbon blocks 68, and an insulating member 72.
  • the carbon block 68 is'suitably bonded to the insulating member 72, the latter bearing at one end against the carbon block 70 to constitute a spacer so that an air gap 74 is established between the carbon blocks 68, 70.
  • the air gap 74 is determined by the minimum arc-over voltage for thich the unit is designed.
  • a fusible solder pellet 76 is interposed between the carbon block 68 and the as-.
  • the upwardly extended parts of the respective contact members 35, 42 lie in grooves 78 (FIG. 4) fomied in a sidewall of the housing 16.
  • Each of these upwardly extending parts of the contact members 35, 42 lie in grooves 78 (FIG. 4) fomied in a sidewall of the housing 16.
  • each contact member 35, 42 constitutes a spring tending to urge the slug 62 toward the cup 64; however, engagement of the cup 64 and slug 62 is prevented, in the normal operation of the protector, by the solder pellet 76.
  • the contact 35 When an over voltage condition of relatively short duration is applied to one of the lines, for example at either pin 25 or at pin 29, the contact 35 provides a conductive path through its upper V" shaped end 80, through slug 62, solder pellet 76 and to carbon block 68. This over voltage transient will arc across gap 74 to carbon block 70 and will be grounded through the strip 45 to the ground pin 27. Under such conditions the solder pellet 76 does not melt. The components of the protector remain in the conditions shown. and FIGS. 2 and 4, and nothing need be done to restore the protector to its normal operating condition. If an over voltage condition appears on the other line, namely the line in which pins 26 and 30 are located, the ground is through the contact 42 and the module 60 associated therewith, all as previously described.
  • the protector will provide a fail-safe operation.
  • the present invention also contemplates a secondary fail-safe grounding path through the conductive strip 45.
  • a secondary fail-safe grounding path through the conductive strip 45.
  • Such condition is shown with respect to the contact 42 and the right hand module 60 in FIG. 3, it being understood that the left hand module will function in like manner.
  • the over current condition causes a heating of the carbon block 70 which'transmits heat through the base of the cup 62 to the conductive strip 45 and the plastic insulating strip 52 associated therewith. If the heat from the carbon block 70 is sufficient in terms of magnitude and duration, the plastic insulating strip 52 will melt causing a direct, low resistance, very short path for shunting current to the ground pin 27.
  • the solder pellet 76 will generally melt to provide the ground connection.
  • Each of the module 60 is fabricated as a selfcontained unit. Consequently, when an over current condition causes either of the module 60 to respond and melt the solder pellet 76, the module 60 may be readily replaced by simply removing the housing 16, withdrawing the spent module, and inserting a new module in its place. Since the insulating strip 52 does not melt in every over current condition, replacement of the strip 45 is frequently not necessary However, if that is required, a new base unit 15 with assembled pins and contacts, such is shown in FIGS. 5 and 6 can be readily assembled with one or more new modules 16 and then further assembled with the housing 16.
  • FIGS. 8-12 show a modified form of the invention in I which like reference numerals indicate like parts previously described with respect to the form of the invention shown in FIGS. 1-7.
  • module 60a includes slug 62a, cup 64a,
  • carbon blocks 68a, 70a, insulating member 72a and fusible solder pellet 76a The arrangement is generally similar to that of the module 60, previously described, except for certain dimensions of the parts.
  • the carbon block 70a is shorter than the block 70 and the slug 62a is somewhat shorter than the slug 62.
  • Seated on the upper surface of the slug 62a is a volute spring 84, for purposes presently more fully ap pearing.
  • line pin 25 is mechanically and electrically connected to the base of terminal 86 which extends upwardly along the inside of the housing 16 for engagement with a printed circuit 88 on a printed circuit board 90 of insulating material.
  • the printed circuit 88 extends downwardly to the bottom edge of the printed circuit board 90 and across the latter and upwardly for a short length 91 on the opposite side of the printed circuit board 90.
  • the part of the printed circuit 88 along the lower edge of the 'board 90 is in electrical and mechanical contact with the upper end of the conductive volute spring 84.
  • the upper end of the printed circuit board 90 has an extension 93that projects through the opening 20 in the neck 18 of the housing.
  • the line pin 29 is mechanically and electrically connected to an additional contact 87 which is similar in construction to the contact 86 and extends upwardly withinthe housing 16 for contact with a printed circuit 95 on the printed circuit board 90. Electrical connection is established between the two printed circuits 88, 95 through a heat coil assembly/-97, which may be of the general type shown in the aforesaid U. S. Pat.No. 3,587,021.
  • Line pins 26 and 30 are connected respectively to identical contacts 99 (one being shown in FIG. 12), the contacts 99 also being identical to the contacts 86, 87.
  • the respective contacts 99 engage printed circuits 88a and 95a (FIG. 11) onprinted circuit board 90a, all being similar to the corresponding element 88, 90, 95, previously described.
  • Printed circuit boards 90, 90a are spaced apart as shown in FIG. 12.
  • circuit board 90a has a reduced extension 930 that is similar to the extension 93.
  • electrical connections to the two printed circuits 88a, 95a is through a heat coil assembly 97a, which is identical to the heat coil assembly 97.
  • the volute spring 84 in the left hand module 60a, FIG. 12, makes electrical and mechanical contact with the lower edge of the printed circuit 88a.
  • Ground pin 27 and alarm pin 31 are alsoconnected to contacts 101 (one being shown in FIG. 12) for engagement with the circuit board 90, 90a. However, in
  • contacts 101 engage the circuit board 90, 90a at regions outside of the printed circuits thereon. So that the contacts 101 may engage both circuit boards, the upper ends thereof are bifurcated as best seen in FIG. 12. The remaining contacts 86, 87, 99 previously described, may also be bifurcated.
  • the heat coil assembly 97 includes a metal sleeve extending through the printed circuit board 90 and being pressfitted or otherwise suitably held for a nonrotatable fit therein.
  • a length of resistance wire 182 has one end connected electrically to the printed circuit 88, the wire 182 also being wound about the sleeve 180. The other end portion of the wire 182 passes through an aperture 184 to the opposite side of the printed circuit board 90, where that other end of the wire is connected electrically to the printed circuit 95.
  • a rotatable shaft 190 extends through the sleeve 180 and on the front side of the printed circuit board 90 the shaft 190 carries a ratchet wheel 192, the latter being spaced from the front surface of the printed circuit board 95.
  • the other printed circuit board 90a has a similar rotatable shaft 190a and a ratchet wheel 192a.
  • a layer of fusible material (not shown) is located between the metal sleeve 180, 180a and the associated rotatable shaft 190, 190a.
  • the fusible material is in its unheated or solidcondition, shafts 190 and 190a are held rigidly within the associated. sleeve 180, 180a.
  • the heat coil of that circuit develops sufficient heat to melt the fusible material permitting the associated ratchet wheel to rotate.
  • the printed circuit board 90 or 90a will be moved outwardly by the force of the associated volute spring 84.
  • the printed circuit boards 90, 90a are held in their respective inward positions against the forces of the volute springs 84, .84 by a latch arrangement that includes a latch support 194 having slots 195, 196 therein.
  • the sleeves 180, 180a extend through the slots 195, 196 so that the slots permit relative movement between the latch support 194, which remains stationary and one or both of the printed circuit boards 90, 90a.
  • the central portion of the latch support 194 carries a U-shaped latch I98 which has two tines 200(FIG.
  • the latch'l98 maintains the printed circuit boards in their normal operating conditions in the protector in opposition to the forces of the volute springs 84, 84.
  • the ratchet wheels are permitted to rotate due to softening of the fusible material in one or more of the heat coil assemblies 97, 97a one or both of the volute springs 84, 84, as the case may be, permits one or more of the ratchet wheels to rotate, thereby moving the associated printed circuit board upwardly as shown with respect to the circuit board 90a in FIG. 12.
  • the protectors of FIGS. 8-12 respond to an over voltage transient by an arc across air-gap 74 for grounding through the base of cup 64a and conductive strip 45, which is connected to ground pin 27.
  • an over voltage of long duration will melt the solder pellet 76a whereby the volute spring 84 will force the slug 62a into contact with the upper edge of the cup 64a to esbase of the cup 64a, melting the insulating strip 52 to provide a secondary grounding path for fail-safe operation.
  • said protector having a base of insulating material, first and second conductive terminals mounted on said said first and second terminals to provide a line circuit through said protector, a conductive ground terminal, and a shunt circuit for over voltage and over current fault conditions in said line circuit;
  • said shunt circuit including normally spaced apart contact members, one of said contact members being in conductive connection with said ground terminal, spaced blocks defining an air gap, springmeans urging said contact members toward their engaged positions, and a solder element that normally maintains said contact members apart in opposition to said spring means, whereby an over voltage of short duration at either of said first'or second terminals produces an are at said air gap.
  • a grounding strip conductively connected to said ground terminal and to .one of the contact members and forming part of said shunt circuit, and an insulating strip interposed between said line circuit and said grounding strip for melting upon heating provide an auxiliary, low' resistance, short current path from said line circuit through said grounding strip and to said ground terminal.
  • said one contact member being a cup-shaped piece that contains one of said spaced blocks such that heating of said one spaced block in turn heats said contact member in said over current condition.
  • said one contact member being amp and the other contact member being a slug, an insulating sleeve surrounding said cup and slug, and said spaced blocks and solder el- 9 ement being within said insulating sleeve, the slug being movable in said sleeve upon melting of said solder ele ment.
  • grounding strip being a generally T-shaped piece with the insulating strip being bonded thereto.
  • said spring means being a contact constituting said means forming the conductive connection between said first and second terminals.
  • said means forming a conductive connection between said first and second terminals including aboard having printed circuits thereon and a heat responsive mechanism operable to break said conductive connection of said line circuit in an over current condition thereof, said volute spring engaging said printed circuit and imposing force on said board.
  • a line protector for communication circuitry, said protector having a line circuit with terminals and conductive means connecting said line terminals, a
  • said spring means including -a volute spring
  • said protector also including a circuit board of insulating material with printed circuits thereon, said printed circuits being in said line circuit, and said volute spring being in said other shunt circuit and engaging said board and being in conductive connection with a printed circuit thereon.
  • said spring means comprising a metallic portion forming said conductive means, said spring means having opposed end portions with said contact members con fined therebetween.
  • a line protector for communications circuitry said protector having a line circuit with terminals and conductive means connecting said line terminals, a ground terminal, and a shunt circuit from said line circuit to said ground terminal and responsive to an over current fault at either of said circuit terminals, said shunt circuit including a grounding strip and an insulating strip laminated thereto, said insulating strip normally interrupting said shunt circuit, and means adjacent to said insulating strip and responsive to an over current condition in said line circuit for melting said insulation strip and closing said shunt circuit; said means adjacent to said strip also includes a spring-pressed member in another shunt circuit from said line circuit to said ground terminal for urging said grounding strip into electrical contact with said conductive means that connects said line terminals to provide a lowresistance short current path from the line circuit to said groun terminal.
  • a line protector for a communications circuitry, said protector having a line circuit with terminals and conductive means connecting said line terminals, a ground terminal, and a shunt circuit from said line circuit to said ground terminaland responsive to an over current fault at either of said circuit terminals, said shunt circuit including a grounding strip and an insulating strip laminated thereto, said insulating strip normally interrupting said shunt circuit, and means ad jacent to said insulating strip and responsive to an over current condition in said line circuit for melting said in sulation strip and closing said shunt circuit; said means adjacent to said strip also including a component in another shunt circuitfrom said line circuit to said ground terminal and responsive to an over current fault in said line for heating said insulating strip.

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US00187018A 1971-10-06 1971-10-06 Line protector for a communication circuit Expired - Lifetime US3794947A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US18701871A 1971-10-06 1971-10-06

Publications (1)

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US3794947A true US3794947A (en) 1974-02-26

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ID=22687278

Family Applications (1)

Application Number Title Priority Date Filing Date
US00187018A Expired - Lifetime US3794947A (en) 1971-10-06 1971-10-06 Line protector for a communication circuit

Country Status (12)

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US (1) US3794947A (enrdf_load_stackoverflow)
JP (1) JPS569861B2 (enrdf_load_stackoverflow)
AR (1) AR193900A1 (enrdf_load_stackoverflow)
AU (1) AU467786B2 (enrdf_load_stackoverflow)
BR (1) BR7206928D0 (enrdf_load_stackoverflow)
CA (1) CA952579A (enrdf_load_stackoverflow)
DE (1) DE2248047C2 (enrdf_load_stackoverflow)
FR (1) FR2156094B1 (enrdf_load_stackoverflow)
GB (1) GB1383578A (enrdf_load_stackoverflow)
IT (1) IT966211B (enrdf_load_stackoverflow)
SE (1) SE388715B (enrdf_load_stackoverflow)
ZA (1) ZA727157B (enrdf_load_stackoverflow)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4862314A (en) * 1988-06-03 1989-08-29 Reliance Comm/Tec Corporation System for providing power to a central office protector module with alarm indicator and including remote alarm indication
US4876626A (en) * 1988-06-03 1989-10-24 Reliance Comm/Tec Corporation Central office protector module with alarm indicator
US4901188A (en) * 1988-12-30 1990-02-13 Reliance Comm/Tec Corporation Line protector with spring
US5195015A (en) * 1991-03-07 1993-03-16 Reliance Comm/Tec Corporation Line protector for a communications circuit
US5751533A (en) * 1996-02-01 1998-05-12 Reltec Corporation Cup and diode assembly for overvoltage protectors and communications lines
US5910877A (en) * 1997-11-17 1999-06-08 Reltec Corporation Line protector for a communication circuit
US20070174700A1 (en) * 2006-01-25 2007-07-26 Honeywell International Inc. Connector ports for anti-tamper
US20140118102A1 (en) * 2012-10-29 2014-05-01 Sean Iwasaki Telecommunication surge protector system

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3743888A (en) * 1972-08-24 1973-07-03 Reliable Electric Co Line protector for a communication circuit
JPS5252636U (enrdf_load_stackoverflow) * 1975-10-15 1977-04-15
JPS5741894Y2 (enrdf_load_stackoverflow) * 1977-09-29 1982-09-14
JPS5693240A (en) * 1979-12-27 1981-07-28 Nippon Electric Co Line protector
JPS642510Y2 (enrdf_load_stackoverflow) * 1981-02-04 1989-01-20
DE3430922A1 (de) * 1984-08-22 1986-03-06 Krone Gmbh, 1000 Berlin Ueberspannungsableiter- und stromsicherungs-magazin fuer mit loet-, schraub- und abisolierfreien anschlusskontakten mit polytropem luftspalt, d.h. lsa-plus kontakten bestueckte lsa-plus-trennleisten der fernmeldetechnik
DE4026004A1 (de) * 1990-08-14 1992-02-20 Krone Ag Schutzschaltung und schutzstecker in telekommunikationsanlagen

Citations (6)

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Publication number Priority date Publication date Assignee Title
US845010A (en) * 1902-04-21 1907-02-19 Rolfe Electric Company Electrical protective apparatus.
US1726807A (en) * 1924-05-01 1929-09-03 Reliable Electric Co Discharge block
US2179935A (en) * 1937-05-28 1939-11-14 Philip J Kayatt High potential cut-out
US2219705A (en) * 1939-01-11 1940-10-29 Jno E Leake Fuse
US3255330A (en) * 1962-08-30 1966-06-07 Cook Electric Co Line protector
US3587021A (en) * 1969-07-22 1971-06-22 Reliable Electric Co Line protector for a communications circuit

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1457249A (en) * 1921-07-12 1923-05-29 Western Union Telegraph Co Electrical protector

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US845010A (en) * 1902-04-21 1907-02-19 Rolfe Electric Company Electrical protective apparatus.
US1726807A (en) * 1924-05-01 1929-09-03 Reliable Electric Co Discharge block
US2179935A (en) * 1937-05-28 1939-11-14 Philip J Kayatt High potential cut-out
US2219705A (en) * 1939-01-11 1940-10-29 Jno E Leake Fuse
US3255330A (en) * 1962-08-30 1966-06-07 Cook Electric Co Line protector
US3587021A (en) * 1969-07-22 1971-06-22 Reliable Electric Co Line protector for a communications circuit

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4862314A (en) * 1988-06-03 1989-08-29 Reliance Comm/Tec Corporation System for providing power to a central office protector module with alarm indicator and including remote alarm indication
US4876626A (en) * 1988-06-03 1989-10-24 Reliance Comm/Tec Corporation Central office protector module with alarm indicator
US4901188A (en) * 1988-12-30 1990-02-13 Reliance Comm/Tec Corporation Line protector with spring
US5195015A (en) * 1991-03-07 1993-03-16 Reliance Comm/Tec Corporation Line protector for a communications circuit
US5751533A (en) * 1996-02-01 1998-05-12 Reltec Corporation Cup and diode assembly for overvoltage protectors and communications lines
US5910877A (en) * 1997-11-17 1999-06-08 Reltec Corporation Line protector for a communication circuit
US20070174700A1 (en) * 2006-01-25 2007-07-26 Honeywell International Inc. Connector ports for anti-tamper
US20140118102A1 (en) * 2012-10-29 2014-05-01 Sean Iwasaki Telecommunication surge protector system

Also Published As

Publication number Publication date
JPS569861B2 (enrdf_load_stackoverflow) 1981-03-04
AU4746672A (en) 1974-04-11
JPS4844743A (enrdf_load_stackoverflow) 1973-06-27
ZA727157B (en) 1973-06-27
BR7206928D0 (pt) 1973-09-13
SE388715B (sv) 1976-10-11
CA952579A (en) 1974-08-06
AU467786B2 (en) 1975-12-11
DE2248047C2 (de) 1985-05-02
AR193900A1 (es) 1973-05-31
IT966211B (it) 1974-02-11
FR2156094A1 (enrdf_load_stackoverflow) 1973-05-25
FR2156094B1 (enrdf_load_stackoverflow) 1978-03-03
GB1383578A (en) 1974-02-12
DE2248047A1 (de) 1973-04-12

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