US3919705A

US3919705A - Loop cord alarm system

Info

Publication number: US3919705A
Application number: US329465A
Authority: US
Inventors: Joseph L Stendig; Claude A Davis
Original assignee: Individual
Current assignee: Individual
Priority date: 1973-02-05
Filing date: 1973-02-05
Publication date: 1975-11-11
Anticipated expiration: 1992-11-11

Abstract

A protection system for preventing unauthorized removal of electrical appliances which employs one or more continuous conductive loops extending to the appliance from its plug. An electrical outlet receptacle having contacts for receiving the plug of the appliance, has the solenoid of a relay and an indicator connected in series through the receptacle contacts and the one or more continuous loops, with the complete series circuit formed thereby energized by the power lines to the outlet receptacle. The relay contacts are disposed in an indicator circuit, such that opening a conductive loop by the removal of an appliance actuates the relay contacts to generate an alarm indication.

Description

United States Patent 11 1 Stendig et al.

' [451 Nov. 11,1975

[5 1 LOOP CORD ALARM SYSTEM Appl. No: 329,465

152] U.S. Cl 340/280; 340/256; 339/l [3 R; 3 l7/l23 {5 ll Int. CL .4 G08B 21/00 {58} Field of Search 340/280, 256. 216; 3l7/l05. [08, H1). l l0. l23', 339/1 13 R. l l3 L {56] References Cited UNlTED STATES PATENTS 1045.226 7/l962 Tra ner 340/280 3.289194 101966 King r i a i 340/380 3 425U5U H1969 Tellerman r r r r 340/256 3.440.636 4/l969 Sliman 340/280 3537.095 lU/l970 Cones r i r r v r i 340/280 ALARMS lhlhllhi ll W71 Trip r 340/280 Primal [:Iumzirmr-John W. Caldwell AAA/slum E.\1/m1'rwr-William M. Wannisky Arm/nay. Agmu, or Firm-Anthom A O'Brien ABSTRACT A protection system for preventing unauthorized removal of electrical appliances which employs one or more continuous conductive loops extending to the appliance from its plug An electrical outlet receptacle having contacts for receiving the plug of the appliance. has the solenoid of a relay and an indicator connected in series through the receptacle contacts and the one or more continuous loops with the complete series circuit formed thereby energized by the power lines to the outlet receptacle, The relay contacts are disposed in an indicator circuit such that opening a conductive loop by the removal of an appliance actuates the relay contacts to generate an alarm indication,

7 Claims. 9 Drawing Figures US. Patent Nov. 11, 1975 Sheet 1 of3 3,919,705

ZO C) H i n 'HT U.S. Patent Nov. 11, 1975 Sheet 2 of3 3,919,705

ALARMS FIG? US. Patent Nov. 11, 1975 Sheet 3 0f 3 3,919,705

LOOP CORD ALARM SYSTEM BACKGROUND OF THE INVENTION l. Field of the Invention The present invention relates generally to protection systems for preventing the unauthorized removal of electrical appliances and more particularly to such protecting systems wherein the appliance is energized by a conductive loop.

2. Description of the Prior Art The use of protection systems which employ conductive loops both to energize an appliance to be protected and to form part of an appliance removal sensor is generally known. as exemplified by U.S. Pat. Nos. 3 ol8.()65; 3.537.095 and 3.1 M1904. In each of these patents. the removal of the appliance plug from its outlet receptacle or the severance of the appliance cord effects the opening ofthe conductive loop and thereby triggers an alarm. However. such systems are limited in application and are subject to high failure rates because of their simplified approach to the problem of unauthorized removal of appliances. and an accomplished and knowledgeable burglar may easily frustrate their opera tion by decoding the protection circuitry employed and thereafter create substitute conductive loops for those to be opened during removal of the appliance. thereby preventing an alarm indication.

SUMMARY OF THE INVENTION Accordingly. it is an object of the present invention to construct a highly reliable protection system for preventing unauthorized appliance removal.

Another object of the invention is to produce a protection system having capability of protecting a plurality of electrical appliances energized from a single outlet receptacle.

Still another object of this invention is to provide an outlet receptacle having a tamper responsive indicator.

The present invention is summarized in a system for detecting unauthorized removal of electrical appliances. an electrical outlet for use in such system. and a loop cord for use in such system. the system including an outlet receptacle having a pair of contacts adapted to be energized by a pair of AC. power lines and another contact. with all contacts mutually insulated from each other. signal responsive means connected between one contact of the pair of contacts and the another contact for providing an indication as to a given signal status. plug means having a pair of prongs and another prong adapted to mate with the pair of contacts and the another contact. respectively. of the outlet receptacle. conductor means connected to the one of the pair of prongs which is adapted to mate with the one contact of the pair of contacts having the signal responsive means connected thereto and extending to a plurality of appliances for energizing same. and conductive loop means connected between the remaining two prongs and extending to the plurality of appliances for energizing same. whereby opening the conductive loop such as during the removal of at least one of the appliances causes the signal responsive means to provide an output indication.

Other objects and advantages of the present invention will be more fully apparent from the following description of the preferred emobdiments when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a loop cord for an appliance in accordance with the present invention.

FIG. 2 is another emobdiment of a loop cord for an appliance in accordance with the present invention;

FIG. 3 is a front view of a receptacle accomodating a schematically represented loop cord ;system for plural appliances in accordance with the present invention;

FIG. 4 is a back view of the receptacle of FIG. 3 including a schematically represented alarm system;

FIG. 5 is another embodiment of a loop cord in accordance with the present invention;

FIG. 6 is an end view of a plug of FIG. 5;

FIG. 7 is a schematic circuit diagram of a complete multi-loop protection system in accordance with the present invention;

FIG. 8 is a schematic circuit diagram of another embodiment ofa multi-loop protection in accordance with the present invention; and

FIG. 9 is a side view. with parts removed of a tamperproof receptacle in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to FIG. 1, a basic loop cord in accordance with the present invention includes a conventional electrical plug having a plurality of

conductive prongs

22, 24 and 26 extending therefrom in mutually insulated relationship for reception by a socket of a power outlet receptacle. An electrically conductive loop 28 is connected between

prongs

22 and 24. while a conductor 30 is connected to prong 26 with all connections made within the body of plug 20 in any conventional manner. Loop 28 may be formed by intorducing a deliberate short between two conductors for a conventional three conductor cord or by actually looping a single conductor between

prongs

22 and 24. Both loop 28 and conductor 30 are encompassed by insulation 32. shown partially removed. which may be rubber. for example. The loop 28 preferably extends into the housing of an appliance 34 such as a television set having a pair of input terminals to be energized; and connects to one of said input terminals. with conductor 30 connected to the remaining input terminal.

Another emobdiment of a loop cord. shown in FIG. 2, employs multiple loops. As shown. plug 20 has been modified such that plug prong 24 has been replaced by a prong having two separate contacts 36 and 38 having insulation 40 therebetwecn. resulting in a four contact plug. Loop 28 now connects between prong 22 and prong Contact 36 and another loop 42 connects between prong 26 and prong 38 with all connections made within plug body 20 in any conventional manner. Both loops are covered by insulation 32, shown partially removed. and preferably extend into appliance 34 where they connect to the power input terminals of the appliance 34.

A protection system employing a loop cord having a single loop to protect a plurality of electrical appliances or the like is shown in FIGS. 3 and 4. the system includes a power outlet receptable 50, the front of which is shown in FIG. 3 and the back of which is shown in FIG. 4, in the interest of clearly showing the complete electrical circuitry associated therewith. Outwardly. receptacle appears to be a conventional three prong plug receiving type. containing two

plug receiving sockets

52 and 54 each having a set of mutually insu- 3 lated plug receiving contacts therein. with each set of contacts including an opposed pair of

contacts

56 and 58 and another contact 60. in respective spaced prong receiving openings. the latter contact having previously acted as a ground connection in the conventional use of this ty pc receptacle but which has now been modified by eliminating its connection to ground in the use of this invention. The pair of

contacts

56 and 58 are electrically connected to

respective terminals

62 and 64. each having a pair of

terminal screws

66 and 68 therein. A pair of incoming l It) volt AC. power lines 70 are also connected to

terminals

62 and 64 via

screws

66 and 68 to accordingly energize

contacts

56 and 58.

A plug. such as that shown in FIG. I having a loop 28 and a conductor connected to its contacts 22. 24 and 26. is schematically represented to be inserted in socket 52 of power outlet receptacle as shown in FIG. 3. Loop 28 and conductor 30 extend into the housing of each electrical appliance to be energized and protected. such as medical equipment 72 containing a motor to be energized thereby. another motor appliance 74. machinery 76 and television set 34. Loop 28 may also contain one or more series switches therein. such as fuses 78. S0 and 82 which may be in series with the electrical appliances associated therewith for protecting same in a conventional manner or as condition responsive switches. indicated as 84 and 86. which may respond to any given conditions. such as the opening or closing of movable partitions including doors and windows.

Equipment which need not be protected. indicated generally at 88, may also be energized from loop 28 and conductor 30 by extending a conductor line 90 thereto from loop 28 in conjuction with conductor 30.

A relay I02, affixed to the back of power outlet receptacle 50. as shown in FIG. 4. includes a solenoid [04 connected between contact and terminal 62 and an armature I06 positionable by a rod I08 fo ferromagnetic material movably disposed within solenoid 104 to selectively actuate a set of relay contacts IIO.

An alarm system is coupled to relay contacts I10 via a terminal block I12 and includes a voltage supply I I4. such as a battery. in series with an indicator 116 which may be a light connected in the panel of a monitor console or switchboard [18 positioned at a central office. The indicator 116 may also indicate when a telephone 120 in the room having the protection system therein has its handset removed from its resting position. thereby closing a switch (not shown) to indicate that a call is desired to be made.

In the operation of the protection system of FIGS. 3 and 4, all appliances are connected to socket 52 of power outlet receptacle S0 to receive cnergization therefrom. with the

fuses

78, 80 and 82 and door and window switches 84 and 86 initially in their normally closed or short circuit state resulting in a complete and continuous loop between

socket contacts

58 and 60, which is energized at power line voltage. such as I II) or 220 volts A.C.. with respect to socket contact 56 which is preferably the reference or ground for the electrical system. Solenoid 104 is initially energized to thereby cause armature I06 to bias relay contacts I10 apart thereby opening the current flow path for light indicator I16 causing it to initially assume a nonilluminated state.

When the loop is opened such as by any of fuses 78. and 82 changing to an open circuit state due to excess current therethrough. or the door or window switches 84 and 86 opening due to an unauthorized entry through a door or window. or the loop being cut or borken during the unauthorized removal of one of the protected electrical appliances 72 74. 76 and 34. solenoid I04 becomes deenergized causing armature 106 to pivotally retract to thereby enable relay contacts I10 to close. Such closure establishes a complete cur rent loop for voltage supply [I4 through relay contacts 110 and light indicator I16 causing it to illuminate as an indication of trouble.

Since the loop does not extend to the unprotected equipment 88, it should be apparent that unauthorized removal of such unprotected equipment by cutting or breaking conductor 30 or conductor line anywhere along their lengths will not cause the loop to be opened and accordingly, light 116 will remain in a non-illuminated state and no indication of such removal will result.

The multiple loop cord of FIG. 2 may also be utilized in the protection system of FIGS. 3 and 4 in place of the single loop cord of FIG. I by merely modifying socket contact 60 into a pair of mutually insulated socket contacts which would then mate with plug contacts 36 and 38 when inserted therein. Solenoid I04 of relay I02 would then be electrically connected across the pair of mutually insulated socket contacts to thereby form a series circuit including one loop 28. the solenoid I04 and the other loop 42 across the input power lines 70 via

terminals

62 and 64. Either one or both loops may extend into the housing of the appliances to be protected. In operation. solenoid I04 is in an initially energized state with its contacts initially open thereby causing light I I6 to be non-illuminated as long as both

loops

28 and 42 remain intact. The breaking or opening of one or both loops removes the solenoid 104 cnergization causing its contacts to close to thereby illuminate light I16 in the manner described above.

A loop cord employing three loops is shown in FIGS. 5 and 6. Plug 200 has eight mutually insulated prong contacts. designated I8. respectively. and is config ured like the plug of FIG. I but modified to the extent that each of

prongs

22 and 26 has been replaced by two separate insulated prong contacts. designated 5. 6. 7 and 8, while prong contact 24 has been replaced by four mutually insulated prong contacts 1-4. A conductive loop 202 extends between prong contacts 3 and 4 of plug 200. Two additional

conductive loops

204 and 206 extend between

contacts

2 and 7 and between contacts I and 8. respectively. while a pair of

conductors

208 and 210 extend from

prong contacts

5 and 6. respectively. with conductor 210 being a dummy conductor. It should be understood that loops 202. 204 and 206 and

conductors

208 and 210 may be rearranged in any number of different configurations relative to prong contacts 1-8 since the receptacle receiving the loop cord will be wired in any of many possibly wiring arrangements so as to be complementary to the circuitry of the loop cord in accordance with the principles of the present invention. and for any given arrangement the loop cord will be encompassed by suit able insulation which may be molded thereabout to form a molded cord construction. which disguises the wiring pattern to frustrate decoding of same by a burglar.

FlCi. 3. normally intended to receive conventional three prong plugs. but now modified by subdividing each set of plug receiving contacts in a socket into eight insulated contacts. designated 1-8 and 946. respectively. each set corresponding in numerically ascending order to prong contacts 1-8 of plug 200 to be received thereby.

One receptacle socket 252 is internally wired to electrically unite contact pairs 1 and 7. 2 and 3. and 4 and 5. respectively. as shown in dotted lines. A relay 256 having a solenoid 258. switch contacts 260 and an armature 262 is mounted on the back of receptacle 250 and has its solenoid 258 connected between

contacts

5 and 6 of socket 252. The other receptacle socket 254 is likewise internally wired in the same manner as socket 252 to electrically unite contact pairs 9 and 15. 10 and I1. and 12 and 13. respectively. also shown in dotted lines. and another relay 264 having a solenoid 266. switch contacts 268. and an armature 270 is mounted on the back of receptacle 250 and has its solenoid 266 connected between contacts 13 and 14 of socket 254. Both sets of

switch contacts

260 and 268 are each connected to a

separate alarm system

272 and 274 such as that shown in FIG. 4.

Contacts 6 and [4 are also electrically connected to receptacle terminal 276. and contacts 8 and [6 are electrically connected to another receptacle terminal 278.

Terminals

276 and 278 are energized by a pair of incoming 1 10 volt AC. power lines (not shown) con nected thereto via

terminal screws

280 and 282. respectively.

The above-described wiring associated with

sockets

252 and 254 each forms a complementary circuit to that of the loop cord of FIGS. 5 and 6. shown with plug 200 inserted in one of the receptacle sockets. such as socket 252. and schematically represented by solid lines and including the three externally

disposed loops

202, 204 and 206 and conductor 208 which terminate in an appliance such as a soda vending machine 284. A complete series circuit is formed which includes

loops

202, 204 and 206. relay solenoid 258 and the power lines associated with

receptacle terminals

276 and 278. Another loop cord may be inserted in socket 254, having three externally disposed loops 286. 288 and 290 and conductor 292 which terminate in another appliance to be protected such as an ice vending machine 294. to thereby form a series circuit which inculdes loops 286. 288 and 290. relay solenoid 266 and the power lines associated with

receptacle terminals

276 and 278.

The operation of the protection system of FIG. 7 is similar to that of the protection system of FIGS. 3 and 4 in that the opening of the series circuit associated with socket 252 such as by cutting or breaking any of the loops 202. 204 and 206 or by removing the plug 200 associated therewith will cause the normally open contacts 260 or relay 256 to close thereby causing the alarm system associated therewith to provide an appropriate indication of trouble. Likewise. the opening of the series circuit associated with socket 254 will cause the normally open relay contacts 268 associated therewith to close and cause an alarm indication in similar fashion.

As an optional feature. the pair of

relays

256 and 264 and associated

alarm systems

272 and 274 may be replaced by a single relay and alarm system. wherein the coil of the single relay would be connected across contact 5 of sockets 252 and contact 13 of socket 254.

6 thereby putting all of the above described loops in a single series circuit with the relay solenoid and the power lines associated with

receptacle terminals

276 and 278. such that opening the circuit will cause the relay contacts to close to energize the alarm system.

Another system for protecting a plurality ofclectrical appliances is shown in FIG. 8. This system also employs a receptacle 300 having a pair of

sockets

302 and 304. each having eight insulated contacts number 1-8 and 9-16. respectively. with contact l6 being electrically connected to receptacle terminal 306 and contacts 6 and 13 electrically connected to receptacle terminal 305. The receptacle 300 is internally wired to electrically unite contact pairs 1 and 4. 2 and 5. 3 and II. 7 and 8. 9 and l2. l and l3. l0 and 15. and 13 and I4. respectively. as shown in dotted lines. while also having the solenoid 307 of a relay 308 connected across contacts and 6 Relay 308 includes a set of armature controlled contacts 310 connected to an alarm system 311 such as that shown in FIG. 4.

A l6 contact loop cord. which simultaneously mates with both sockets. employs a plurality of loops at least commensurate in number to the number of appliances to be protected and may take the form of an octopus type cable having an integral section having a single termination for reception by receptacle 300 and a plurality of branches extending from the integral section. each including a pair of conductors. one of which is a loop. which extend to an appliance to be protected to energize and protect same. An ice vending machine 310 to be protected has both a loop 312 formed bctwecn plug contacts I and 8 and a conductor 314 from plug Contact 6 extending therein to energize same. Another loop 316 between

plug contacts

2 and 7 along with a conductor 318 from plug contact extends into a soda vending machine 320. Still another loop 322 between plug contacts 3 and 4 along with a conductor 324 from plug contact 15 extends into a television set 326 to be energized. A coffee vending machine 328 is energized via a loop 330 extending therein from plug contacts 9 and 16 and a conductor 332 from plug contact 13. and a milk vending machine 334 is likewise energized via a loop 336 extending from plug contacts 11 and 12 and a conductor 338 from plug contact 14.

Operation of the FIG. 8 protection system is similar to that of the previously described protection systems in that the switch contacts 310 of relay 308. which are initially open. close upon the breaking of the circuit including the loops to control the alarm systems 31] connected across the switch contacts 310 in a manner as already described above.

FIG. 9 shows a receptacle having a tamper proof feature which is advantageously utilized in the protection systems previously disclosed. The rcceptable of FIG. 9

' is shown to be the type which receives three prong plugs such as described in FIG. I and incorporated in the protection system of FIG. 3. and will be described accordingly. but such should be considered as merely exemplary. since any receptacle having an external conductor receiving connection block disposed in a wall box or receptacle box. including all of the power outlet receptacles of the protection systems described above. telephone receptacles and the like. may include the tamper proof feature as a part thereof.

As shown. power outlet receptable includes at least one open loop responsive relay such as relay 102 affixed thereto. in addition. a switch 400 which may be a single pole single-throw switch having a contact clos- 7 ing bias is affixed to receptacle 50. Switch 400 includes a housing llffiXCd to the back of receptacle socket 54 although it may be positioned anywhere on the back of receptacle 50.

A shaft. generally indicated at 402. extends through an aperture in the switch housing and is disposed between the rear portion of a wall box or receptacle box 404 and a movable armature 406 of switch 400. Shaft 402 includes a rod 408 which is at least partially threaded externally for reception by an internally threaded head member 410 which includes a flange or collar 412 thereon for retaining head member 410 within the switch housing. The total length of shaft 402 is adjustable and is preselected such that when receptacle 50 and receptacle box 404 are intact in their normal relative position as shown. the armature 406 of switch 400 is retracted against its switch contact closing bias to maintain separation between the switch contacts. The contacts of switch 400 are in shunt with the contacts 110 of relay 102 and accordingly are across the alarm circuit including voltage source 114 and indicator light 116.

In use. both relay 102 and switch 400 have their contacts in a normally open state and one or more ap pliances may be energized from receptacle 50 via a loop cord. In the event of receptacle 50 being tampered with such that it is moved away from the back of the receptaclc box 404. that is. to the right in FIG. 9, switch 400 will likewise be moved an equal amount in the same direction. Shaft 402 will remain generally fixed in position. continuing to abut the receptacle box 404 while armature 406. due to its closing bias. causes the switch contact carried thereby to move closer to its mating switch contact in accordance with the movement of receptacle 50 and switch 400. Sufficient move ment in excess of a predetermined amount will allow the switch contacts to close and thereby establish current flow therethrough from voltage supply 114 to energize light indicator 116 in the same manner as if relay 102 had its contacts 110 closed in response to a broken loop. as an indication of trouble.

The protection systems disclosed herein are generally intended for establishments which have a plurality of rooms or locations containing electrical appliances to be protected against unauthorized removal such as hotels. motels. office buildings. private residences and the like. and accordingly. a plurality of such systems. either identical or different. may be combined in an overall protection system having a central monitor console which includes a plurality of indicators therein. each identified as to a protected location such that a person monitoring the central console may immediately determine the whereabouts of the trouble.

Furthermore, inasmuch as each protection system provides an alarm indication in response to removal of the plug from the receptacle. it is possible to obtain an alarm indication where no unauthorized removal of an electrical appliance is intended. such as when the plug is inadvertently removed from the receptacle by a hotel guest. for example. An alarm indication under such cir cumstances if not properly handled. may result in much embarrassment for all parties concerned along with the generation of ill will and resulting loss of business. Accordingly. provision may be made to fix the plug to the receptacle in the use of this invention such as in the manner disclosed in U.S. Pat. Nos. 3.16] .450 and 3.101.922 in the interest of avoiding such a problem.

The present invention is advantageous in that it has practically unlimited capability insofar as the number of electrical appliances which may be protected against unauthorized removal from a single electrical outlet inasmuch as plural appliances may be protected by a single loop. and loop cords having increased numbers of loops may be utilized with appropriate receptacles designed in accordance with the principles of the present invention. Further. the increased complexity of the protection systems due to the increased number of loops, and accordingly. the increased receptacle wiring commensurate therewith tends to prevent the frustration of such protection systems by a burglar since such increased number of loops and associated series circuitry reduces the likelihood of the system being decoded. especially since many different receptacle wiring arrangements may be employed with any given loop cord.

lnasmuch as the present invention is subject to many variations. modifications and changes in detail, it is in tended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

l. A protection system for electrical appliances comprising:

a plug having at least four mutually insulated prongs extending therefrom;

conductor means extending from the plug to at least one electrical appliance for energizing the one electrical appliance;

said conductor means including a plurality of conductive loops connected across respective pairs of the four prongs and extending from said plug to the one electrical appliance;

receptacle means having at least four contacts in at least three spaced prong receiving openings therein and matable with the respective four prongs of said plug with two of said contacts adapted to be ener gized by a pair of incoming power lines;

indicator means operated by de-energization thereof.

and

circuit means connected to said receptacle contacts for completing a series circuit including a selected arrangement of said plurality of conductive loops. said indicator means and said two contacts when said plug is inserted in said receptacle:

said series circuit including at least one of said loops connected between contacts in different openings of the three receptacle openings;

whereby opening any of the plurality of loops such as during the removal of said one electrical applicance will operate said indicator means.

2. The invention of claim 1 wherein said indicator means includes a current responsive switch which changes state in response to a loss of current flow therethrough due to opening of at least one of the loops. and alarm means responsive to said switch changing state.

3. The invention of claim 1 wherein a plurality of conductive loops extend to the same electrical appliance to be protected.

4. The invention of claim 1 wherein at least one of said plurality of conductive loops extends completely into said electrical appliance.

S. The invention of claim I wherein a plurality of electrical appliances to be protected each have at least one of said conductive loops extending thereto.

6. The invention of claim 5 wherein at least one of said conductive loops extends completely into an electrieal appliance to be protected.

Claims

1. A protection system for electrical appliances comprising: a plug having at least four mutually insulated prongs extending therefrom; conductor means extending from the plug to at least one electrical appliance for energizing the one electrical appliance; said conductor means including a plurality of conductive loops connected across respective pairs of the four prongs and extending from said plug to the one electrical appliance; receptacle means having at least four contacts in at least three spaced prong receiving openings therein and matable with the respective four prongs of said plug with two of said contacts adapted to be energized by a pair of incoming power lines; indicator means operated by de-energization thereof; and circuit means connected to said receptacle contacts for completing a series circuit including a selected arrangement of said plurality of conductive loops, said indicator means and said two contacts when said plug is inserted in said receptacle; said series circuit including at least one of said loops connected between contacts in different openings of the three receptacle openings; whereby opening any of the plurality of loops such as during the removal of said one electrical appLicance will operate said indicator means.

2. The invention of claim 1 wherein said indicator means includes a current responsive switch which changes state in response to a loss of current flow therethrough due to opening of at least one of the loops, and alarm means responsive to said switch changing state.

5. The invention of claim 1 wherein a plurality of electrical appliances to be protected each have at least one of said conductive loops extending thereto.

6. The invention of claim 5 wherein at least one of said conductive loops extends completely into an electrical appliance to be protected.

7. The invention of claim 5 including a plurality of conductors each connected to a different plug prong and each extending to a different electrical appliance to be protected for energizing same.