US2071283A - Supervisory circuit - Google Patents

Description

Feb. l6,` 1937. H. c. GRANT, JR

ySUPERVISORY CIRCUIT original Filed Nov. l21, 1929 INVENTOR Many We!! 0 'dL-M v4- W w ATTORJVEICSV 5 Sheets-Sheet 1 EEDD D D D D DDDUDD U D U D D D U D U U D U D D n-Dn-Un-UDn-UDUU Feb. 16, 1937. H, c. GRANT, JR

SUPERVI SORY CIRCUIT Original Filed Nov. 21, 1929 5 SheetsSheet 2 INVENTR 4 lrmly ranl Jr,

AIToRNElS Feb. 16, 1937. H. czGRANT, .1R v 2,071,283

SUPERVISQRY CIRCUIT l original FiledrNov. 21, 1929 5 sheets-sheei ,s-

+ JNVENTOR Feb. 16, 1937. H. c. GRANT, JR 2,071,283

4 SUPERVISORY CIRCUIT Original Filed Nov. 21, 1929 5 Sheets-Sheet 5 305 INVENTOR bry Comps/ Graf/1- Jr.

ATTO R N EY Patented Feb. 16, 1937 UNITED STATES OFFICE SUPERVISORY CIRCUIT Original application November 21, 1929, Serial Divided and this application November 10, 1931, Serial No. 574,091

3 Claims.

The present application is a division of applicants copending application Ser. No. 408,740 led November 21, 1929, now Letters Patent No` 2,003,358 dated June 4, 1935, for System for indicating the presence and location of iire, and embodies that portion of the system illustrated and described in the above copending application which relates to the supervisory system for the detecting and alarm device. It will be apparent that the circuits for supervising the system described in the above copending application may have wide application and an object of the present invention therefore is to provide a supervisory system for electrical circuits which serves effectively to maintain a constant indication of the condition of a system to be supervised.

Further objects of this invention will'appear as the same is described more fully in connection with the accompanying drawings, wherein:

Figure 1 is a wiring diagram showing schematically a re detecting system constructed in accordance with the present invention.

Figures 2, 3, and 4 are diagrammatic views showing the system of Figure l enlarged.

Figure 5 is a wiring diagram showing schematically the Wheatstone bridge arrangement of the present invention.

Figure 6 is a conventional arrangement of a control cabinet and cabinet door switch employed in the execution of the invention.

Figures '7 and 8 are views of the cabinet door switch shown in Figure 6 Figure '7 being a view of the back of the switch as shown in Figure 6 and with the cover plate removed; and Figure 8 being a view of the bottom of the switch as shown in Figure 6 and with the cover plate removed.

At the outset, the general detecting and signalling system which is supervised in accordance with the present invention will be described in order that the present invention may be more fully understood and its wide application appreciated.

Referring to the above drawings, a battery is indicated at BAT. having its positive terminal connected to a positive bus wire i which includes 5 a battery supervising relay 2, a switch Se having switch points 3 and 4, connections 5 and 6, switch Sm having switch points 'l and 8, and positive bus wire 9. A plurality of external circuits, in which thermostats or other suitable heat operated devices are connected, is used in connection with the system shown and described herein, but for the purposes of description and in the interest of clarity, only two such circuits have been shown.

These circuits have been marked as A and B and one side of each of these circuits is connected to the positive bus wire 9. Since the circuits A and B are identical and are connected to similar relays and associated elements, only the connection for circuit B will be described herein, it being understood that the corresponding elements of circuit A, as well as other circuits, not specically shown, function in the same manner as4 the elements of circuit B. The other side of each external circuit is connected to the negative terminal of the battery and the elements for so connecting these circuits include, in the case of circuit B, a wire I6, a contact l'l, a trouble alarm relay T1, a fire alarm relay M1, wire I8, wire I9, and negative bus wire 20, such negative bus wire being connected to the negative terminal of the batte-ry.

It will thus be seen that a supervisory current flows through the external circuit, the trouble alarm relay T1 and the fire alarm relay M1. If a break should occur in the wire so that current through the trouble alarm relay T1 is interrupted, this relay will be deenergized and will close contacts 2| and 22, causing a trouble alarm lamp L1 to be lighted. Current ows through the trouble alarm lamp L1 from the positive bus wire 9 through the lamp, contact 2|, to connection 23, contact24, and lconnection 25 to the negative bus wire 2G. This light indicates trouble in the external circuit B. At the same time, the general trouble alarm bell T. B. is sounded since it is connected to the positive bus wire through wire I0, point 26, point 21, point 28, point 29, through the bell T. B., point 30, wire 32, points 33, 35, and Sl, contact 22, contacts 38 and 39 of switch S1, point 23 through Contact 24 and point 25, to negative wire 20. In order to clear the general trouble alarm bell so that it may be free to indicate trouble in other circuits, the switch S1 is thrown to the left to make contact at point 40, thus opening the circuit through the general trouble alarm bell and clearing the bell for the indication of trouble in the other circuits. The trouble alarm lamp L1 remains lighted until the trouble has been repaired whereupon the trouble alarm relay T1 picks up its armature thus opening the contacts 2l and 22. The trouble alarm lamp L1 remains lighted, however, by reason of its connection from the positive wire 9 to the successive points 40, 39, 23, 24, and 25. In order to clear the trouble alarm lamp L1, the switch S1 is thrown` to its normal position at the right, as viewed in the fiure, to make contact at point 38.

The battery supervising relay 2 is in series with the circuit supplying current to the external cir-'- cuits, and if the current from the battery should fail, the battery supervising relay 2 will be deenergized and close contacts 4l and 52, thus causing the battery supervising trouble alarm lamp L2 to be lighted and the general trouble alarm bell T. B. to be sounded. Current flows through the trouble alarm lamp L2 from the positive bus wire 9 through wire l0, point 26, point 2l, point 12, point 30E, through the lamp L2, contact lil, and point 302 to the negative line at point 353; while the path of current through the general trouble alarm bell T. B. is from the positive bus wire 9 through wire l0, point 26, point 21, point 28, point 29, point 30, point 304, contact 42, switch Si, and point 3D2 to the negative line at point 363. A switch S1 is provided to clear the general trouble alarm bell in the same manner as that described in connection with the trouble alarm relay T1.

Two fire alarm bells are provided, one supervised and one unsupervised. The supervised fire alarm bell is indicated at S. A., while the unsupervised bell is indicated at U. A. The supervised bell is in series with a relay 43 which is of such resistance as to prevent the ringing of the supervised re alarm bell, at the same time permitting a supervisory current to flow. The supervisory connection is from the positive wire 9 to the successive points 26, 21, and 28, through the supervised re alarm bell to the point lill, through the winding of, the relay 43 and connection E to the point 46 on the negative bus wire 2E). If the supervised alarm bell should become inoperative, the supervising current will fail and the relay i3 will become deenergized, thus permitting the closing of its contacts at 4l and 4S, thus lighting the supervised re alarm bell trouble alarm lamp L3 and sounding the general trouble alarm bell. The switch Se is provided for clearing the general trouble alarm bell in the same manner as that described in connection with the trouble alarm relay T1.

A fuse 22| will be found in one lead to the supervised fire alarm bell. The reason for installing this fuse is that the resistance of the winding of the supervised re alarm bell is ordinarily only a fraction of one percent of the resistance of. the winding of the re alarm bell supervising relay 113. If a short circuit of the supervised fire alarm bell leads should occur, no trouble signal would be given because the short circuit of the winding of the supervised re alarm bell would allow a slightly greater supervising current to flow through the supervising relay, this increase in current not being, however, great enough to blow the fuse 22|. If a re signal should be given. at which time the high resistance of the supervised nre alarm bell supervising relay is cut out of the circuit, the short circuit oi the re alarm bell connecting wires would constitute a direct short circuit across the source of` current and, therefore, the fuse 22 is placed in one lead to the supervised re alarm bell to relieve, immediately, this short circuit condition which otherwise would Seriously aifect the Operation of the other circuits of the system. The blowing out of this fuse places the system in a condition to render a delayed trouble signal in a manner to be described hereinafter.

A resistance 4.9 is connected in the external circuit B at the extreme end thereof and this resistance is of such value as to limit the current which i'lows through the trouble alarm relay T1 and the fire alarm relay M1 to a value below that necessary to cause the iire alarm relay M1 to pick up. If, however, by reason of a re in one of the spaces protected on the circuit B, a thermostat should function and thus short circuit the resistance @9, suicient current will flow through the circuit already described and cause the fire alarm relay M1 to pick up its armature and close contacts at points 50, 5l, 52, and 53, at the same time breaking the contacts at the points ll and 2e. The re alarm relay M1 is so constructed that the Contact 5i will make before the contact il breaks. The purpose of Contact l1 is to connect the resistance of the external circuit across one portion of a Wheatstone bridge as described hereinafter.

The opening of the contact i'! would result in the deenergization of the fire alarm relay M1 were it not for the closing of contact 5| before the opening of Contact Il. By reason of the closing of the contact 5l, a connection is made through the Winding of the iire alarm relay M1 from the positive bus wire 52 to the successive points 54, 55, 55, 5?, wire 58, connection 55, wire Bil, connection Gl through contact 5l, the Winding of re alarm relay M1, wires i8 and i9, to the negative bus wire 2G. The ire alarm relay M1, therefore, remains energized until the circuit through its winding is manually opened in the manned described hereinafter.

Upon the closing of contact 52, relay 62 is energized by reason of its connection to the positive bus wire 9 through wire IG, and connection 26, cabinet door` switch C. D. S. and to the negative line through point 63, wire 5d, through the contact 52, to the point 25. Upon energization of the relay 52, contacts 65, 51 and E8 are closed, while contact 59 is broken. The closing of the contact S8 short circuits the supervised fire alarm bell supervising relay 43 and permits the supervised re alarm bell to sound by reason of its connection from the positive wire to the successive points 26, 2l, and 23 through a wire 1G to the point 4A, through a wire '.l, through contact E3, to the point 25, and thence to the point on the negative line. By reason of the short circuiting of the supervised fire alarm bell supervising relay 43, the relay i3 is deenergized and the contacts lil and (i8 are closed. This would cause trouble alarm lamp L: to light and the general trouble alarm bell to sound if it were not for the fact that the contact B9 of the relay (32 opens the connection from the trouble alarm lamp and from the general trouble alarm bell to the negative line. It will be seen that the trouble alarm lamp circuit is from the positive Wire S to the successive points 26, 21, l2 through the trouble alarm lamp and Contact fil' to a point 73 (where the line from the general trouble alarm bell joins a common return '54), through such common return to the contact E9 and the negative line wire.

The unsupervised nre alarm bell U. A. is caused to ring at the same time as the supervised fire alarm bell, the circuit for accomplishing such ringing being closed through the contact 57. Current flows from the positive wire 9 to the successive points 23, 2l', 23, and 29, through the unsupervised re alarm bell U. A. and through contact 8'! to the negative line. Cloing of the Contact 65 produces an operation which will be described more fully hereinafter.

External circuit re alarm lamps A', B', C', D', E', F', G', H', I', J', K', etc. corresponding to the external circuits A, B, etc. are connected in series with a supervising relay 75. The supervising current flows through a circuit from positive wire 9 through a wire III to a connecnegative line.

tion 16, through a wire |25 to a connection 11, through contact point 18 to connections 19, 80, wire 8|, connections 82 and 83, contact point 84, connections 35 and 86, wire 31, connection 38, contact 89, connection and Wire 9|, connections 62 and 96, contact 64, connections and 95, wire 91, connection 98, Contact 99, connection |66, wire itl, connections |52 and |63, Wire |64, relay 15, connection |95 and Wire |86 to negative wire 20. Since the external circuit fire alarm lamps are in series, if any of the lamps become defective, the supervising current will cease and the relay 15 will be deenergized, closing its contacts |69 and Hl). Closing contact |69 establishes a connection from the positive wire 9 through wire to point 15, through the trouble alarm lamp L4, through the contact |69, point ||2, through wire H6 and contact H4 to wire H5 and the negative wire 2i). At the same time, connection is established from the positive Wire 9 to the successive points 26, 21, 28, and 29 through the general trouble alarm bell to the point 36 through the wire 32 and point 33, wire ||6 to contact im and point I |1, through switch S10 to point |2 and negative wire as described above, thus causing the sounding of the general trouble alarm bell. The switch S10 is provided for clearing the general trouble alarm bell in the manner already described in connection with the trouble alarm relay T1.

At the same time that a ire alarm relay, for example, M1 is energized with consequent energization of the relay 52, a relay H6 is energized by reason of its connection from the positive wire through the wire to the points 'F5 and 11, through the winding or the relay H8 to a point H9 and through a wire |253 to the point 63 which is connected to the negative line through wire B4, contact 52 and point 25. Upon energization of the relay H6, the contacts at 18, 84, 89, 94, 99 and ||4 are broken, while contacts are closed at |2l, |22, |23, |24, and |25. The external circuit re alarm lamp B', corresponding to the external circuit B, is then lighted by reason of its connection from the positive wire 6 through the wire iii to the point l, through wire |25 to point 11, through contact l2! to point 60, through wire 6| to point 82, through contact |22 to point i2?, through contact |23 to point |28, through contact |24 to point 23, through contact |25 to point |92, through wire |ll| and fire alarm lamp B to point |56, through wire |3| to Contact 56, and to connection 25 on the reason that the deenergization of the relay 15 does not result in lighting the trouble alarm lamp la and ringing the general trouble alarm bell upon the breaking of the contacts at 18, 64, 89, S4, 99, and H4 is that the contact |14 is in the line which connects the trouble alarm lamp Li and the general trouble alarm bell to the negative line. When the contact ||4 is opened, the trouble alarm lamp- L4 and the general trouble alarm bell cannot function.

The foregoing description has dealt chiefly with the Various means for indicating trouble and With the means for indicating the particular circuit from which a fire signal has been given. It will be seen that the foregoing construction will function equally well regardless of the number of external circuits and the corresponding fire alarm lamps which are connected therewith. The following description is concerned principally with the means for detecting the exact thermostatic circuit closer which has functioned in the particular external circuit.

A Wheatstone bridge connection (shown in part and more clearly in Figure 5) is provided including resistance elements |33 and |64, the resistance of the external circuit which has been actuated, and a variable known resistance indicated generally at |31. Point |32 of this connection corresponds to Athe connection of the resistance elements to the negative side of a battery circuit while point |36 is the connection to a galvanometer and the unknown resistance which is the resistance of the external circuit. Point |35 is the connection to the other side of the galvanometer and to one terminal of the variable known resistance |31. It will be seen that point |32 is connected through a resistance |38 to points |39, |40, wire Ilil, contact 24B, contact 24| to the negative Wire 25|.

Point |35, on the other hand, is connected to the positive line through wire |44, resistance |45, movable contact Ill-5, point 41, Wire |48, resistance |49, and point |59 to a movable contact |5| and point |52 through wire |53 which is connected to the positive line through point |54 and wire |55 to point 54 and positive wire 9. One side of the external circuit B is connected to the positive line and the other side of the circuit B, upon energization of the fire alarm relay M1, is connected to the point |35 through wire I6, contact 50, point |56, Wire |51, point |58, Wire |59 and point |36.

Upon the occurrence of re in any space, the fire alarm relay, corresponding to the circuit by which such space is protected, is energized. A fire alarm lamp indicating the circuit is lighted and the fire alarm bells are sounded. The resistance of that portion or" the external circuit lying between the positive line and the particular thermostat which has functioned, is brought into proper relation with the Wheatstcne bridge arrangement for permitting the automatic balancing of the resistance of the external circuit and the consequent determination of the particular thermostat which has functioned. The

variable resistance |31 consists of a rotary switch such as is now employed in automatic telephone Work, resistances being connected between each of the adjacent points of the rotary switch. Such rotary switches are of the conventional type now Well known in the art, and in connection therewith specic reference is made to the June 1934 issue of The Strowger Techinal Journal, Volume 3, Number l, published by Associated Electric Laboratories, Inc., oi Chicago, London, and Antwerp; and to the British patent specifications. Nos. 256,606 and 313,667.

With reference to the external circuit B, it Will be seen that the path of the supervisory circuit from the positive wire t is through a compensating resistance |69, a resistance U1, the terminal of a thermostat TT1, a resistance U2, through the terminal of a thermostat TTz, etc. there being similar resistance before each theru mostat. With reference to the variable resistance arrangement |31, the resistance |49 is of the Same Value as the resistance U1; and the resistances R2, R3, R4, etc. are of the same values as the corresponding resistances U2, Us, U4, etc. all of the resistances being of the same value. f, therefore, the contact |46 is moved from the rst point of the rotary switch to any other point, there can be cut into the Wheatstone bridge arrangement, enough resistance to balance the resistance from the external circuit which is thrown in as another leg of the Wheatstone bridge arrangement.

The automatic balancing of the resistance of the external circuit is accomplished through the medium of the Wheatstone bridge arrangement in combination with a galvanometer relay, the relay being so connected to the circuit that its contact remains closed as long as the balancing resistance |31 is less than the resistance of the external circuit. It will be seen that the variable resistance |31 has been shown with the movable contact |45 on the rst point of the rotary switch. This is the normal position of rest at which time only the resistance |139 is in the balancing resistance circuit so that the resistance is always less than the resistance thrown in from the external circuit (except for the first resistance, which will be discussed later on). If, therefore, any thermostat beyond the rst one functions, a resistance greater than the balancing resistance will be thrown across t-he proper leg of vthe Wheatstone bridge, and the galvanometer relay contact i5! will be closed.

As soon therefore, as a 'lre alarm relay, such as M1 is energized, a relay |62 is energized by reason of its connection from the positive wire 9 through the connection 54, line |55, connection |54, wire |53, connection |53, wire E62, contact |65, wire |66, through relay |62, galvanometer contact |6|, wire |4|, contact 2150, contact 24| to the negative wire 2li. When the relay |62 is energized, the contact |1| is closed. rI'his results in energizing relays indicated as Mot. 1 and Mot. 2, by reason of their connection with the positive wire |53 through the motor relay windings, the parallel relay contacts 243 and 254, respectively, wires 265' and 2115 and connection 245, wire 246, connection 241, contact |1|, connection |05 and wire |35 to the negative line wire 20. Upon the closing of the contact |1| of the relay |62, connection is established from the positive line to the negative line. The slow acting relay 231 is thus energized and Contact opened, thus deenergizing relay |52 so that contact 11| is opened and slow acting relay 231 deenergized. This cycle of operation is repeated as long as the galvanometer contact l5! is closed. At the same time that the slow acting relay is deenergized by the opening of the contact |1| of the relay |52, the motor relays Mots. 1 and 2 are deenergized and simultaneously with the deenergization of the motor relays, the movable arm |45 moves one step from the first to the second point of the rotary switch. The same cycle is repeated until the amount of the balancing resistance |31 which has been cut in, is equal to, or greater than, or even somewhat less than, the cut-in portion of the resistance of the external circuit. As soon as this condition is reached, the current iiow through the galvanometer winding either weakens suiiiciently, ceases, or reverses, so that the galvanometer contact |61 is broken, as well as the circuit through the relay |62. The rotary switch has therefore come to a position of rest and can be made to indicate the exact thermostat which has functioned. This will be described in greater detail hereinafter. lNhile in a theoretically perfect circuit the balancing resistance can be considered as exactly balancing the resistance of the external circuit, the resistance of the external circuit might be somewhat less than the proper balancing resistance due to slight negative errors in winding the resistance units U1, U2, etc., while it might be somewhat more than the proper balancing resistance due to more wiring being used in the external circuit than the theoretically correct amount. The galvanometer relay is therefore adjusted to operate over a range such that the correct balancing resistance will be cut in not only when the resistance of the external circuit equals the proper balancing resistance, but also when it is within predetermined negative and positive variations from V'the proper balancing resistance.

On the assumption that the first thermostat has functioned, the lamp il of the tens column and the lamp of the units column will be lighted in the following manner. The positive line wire 9 is connected to all of the lamps of each column and current flows through the proper lamp, in the hypothetical instance the lamp (i, of the tens column to point |14, through a movable contact |15, connection |18, wire |11, and wire |23 to the connection H9, wire |20 and connection 63 to wire 64, and contact 52 to connection 25 on the negative line. At the same time, current flows from the positive wire 9 through the units lamp wire |19, movable contact E3B, and through the connection |16 and path just traced. The connection of the points in the fifth row is such that a single set of lamps will serve for the unit indications, while the connection in the fourth row is such that one lamp is required for each of the tens of the series of thermostats and balancing resistances.

Relay 231 is a very slow acting relay to permit motors and 2 to complete, with certainty, a cycle of operation before a new cycle is instituted. As before described, when galvanometer contact |5| is closed, connection is established from the positive line at |63, through contact |55, wire |65, relay |62 and galvanometer contact |61 to the negative line. Relay |62 is thus energized and contact |1| closed so that connection is established from the positive line at 228, through the winding of the relay 231, through contact |1| and to the negative line. The relay 231 is thus energized and contact |65 opened thus deenergizing relay |62 so that contact |1| is opened and relay 231 deenergized. i

rThis cycle of operation is repeated as long as the galvanometer contact |6| is closed. Each time that contact |1| is closed, connection is established from the positive line through the windings of the rnotor relays and 2 through parallel contacts 2113 and 244, connection 245, wire 246, to the point 221 and through contact |1| to the negative line, thus energizing Mots. 1 and 2. As already explained relay 231 is very slow acting and thus serves to insure complete operation of both motor relays and 2 before relay 231 opens the contact at |55. Such opening results in the deenergization of relay |52 and the opening of contact 51|, which results in the deenergizatlon of the motor relays and 2 and of the slow acting relay 231.

In order to reset the system, the push button switch |55, is operated to make contact with the point 92. Breaking the contact at 55 causes the deenergization of the i'lre alarm relay M1 with the consequent return to normal conditions of the apparatus controlled thereby. Connection is thus established from the positive line at 54 to the point |92, through wire 25|! to connection 25|, through the windings of relay 252 and 253, to points 252 and 255, to the interconnected points of the two rotary switches through wires 254 and 255. From these respective interconnected points, the circuit is completed to the negative line through points 235 and 236. The relays 252 Cil ` in energization of the motor relay l.

and 253 are therefore energized, causing the respective contacts at 24| and 243 for the relay 252, and 249 and 244 for the relay 253 to be broken and contacts 266 and 25? to be closed for the relay 253, while the corresponding contacts are closed for the relay 252. With the closing of the contacts 256 and 251, connection is established from the positive line |53, through points |52 and 232, through contact 251 and line 250, to the point 25|, through the windings of the relays 252 and 253 to the points 254 and 255 to the interconnected points of the rotary switches and thus to the negative line. Even though the push button switch |94 is returned to its normal position in contactwith point 55, the relays 252 and 253 remain energized. until such time as movable cony'tacts |9| and |98 rest upon the rst points of the respective rotary switches. Through the closing of the contact 266 of the relay 253, connection is established from the positive line through the motor relay 2, through the Contact 266, contact |69, to the interconnected points of the rotary switch and thus to the negative line. Corren sponding action occurs for relay 252 and results At the same time, contact |59 is opened and the motor relay 2 is deenergized, causing the advance of the rotary switch one step. After such advance, the contact |69 is again closed and the motor relay is again energized. Such operation continues until the movable contact |9| rests upon the nrst point of the rotary switch. If, for any reason, motor 2 should get out of step with motor motor 2 will not continue to operate its rotary switch but will come to rest because it is no longer energized after the movable contact |9| rests upon the iirst point of the rotary switch. Motor i is therefore free to return the other rotary switch to its initial position without being affected by the action of motor 2.

The switch 268 is a p-ush button switch similar to the push button switch 94 and interconnected with the switch iSd in a series parallel arrangement, and is controlled by the opening of the door of the cabinet in which all of the apparatus is arranged. Upon the occurrence of fire, the re alarm bells sound and the system automatically balances itself. The re watch attendant then runs to the central station and opens the door of the cabinet, thus causing the switch 293 to momentarily close the circuit from the point 56 -to the point |98, causing a resetting action to occur in the same manner as caused by the push button switch |94. As soon, however, as the movable contacts reach the rst switch points, the

re indication is repeated and the i'lre watch attendant can determine from the lamps which are lighted, the space which is are. He can then push down the manual reset push button 94 and reset the system, and when the movable contacts again reach the rst switch points the nre indication will be again given as a check upon the initial reading. This resetting operation can be made as many times as the nre watch attendant desires in order to be sure that the apparatus has functioned properly and that the proper space has been 'indicated After the nre has been extinguished and the thermostat has been renewed, the door of the cabinet can be closed and the system will again be in its normal condition. If it should be forgotten to reset the system by means of the manual push button |94, the closing of the door will accomplish the resetting action through the closing of the push button switch 208.

. Compensating resistances |66 and 209 may be inserted at predetermined intervals in the external circuits, while compensating resistance |45 may be inserted before the movable contact |46 to correspond with the resistance |66, while com-` pensating resistance 2m may be inserted between the fourteenth and fifteenth contacts in the second row of contacts to correspond with the re-y sistance 299.

A door switch C. D. S. is provided in the circuit of the iire alarm bell ringing relay 62, so that upon the opening of the cabinet door the fire alarm bells will stop sounding.

A conventional arrangement of control cabinet and cabinet door switch is shown in Figure 6, wherein the reference numeral 395 represents a spring pressed switch button which is engaged by the door of the control cabinet when closed and which opens the circuit of the fire alarm gongs when the door is opened and the switch button is released. The contact controlled by the switch button 365 is shown at 365 in Figure 8.

Reference has already been made to the reset push button switch 263 which momentarily closes the resetting circuit upon either opening or closing of the control cabinet door. This push button switch can conveniently be combined with the cabinet door switch C. D. S. and is so shown at 268 in Figures 6 and '7. In order to momentarily close the resetting circuit, a bracket 301, provided with a camelike lower surface 3628, is mounted on the control cabinet door in such a position that the cam surface engages the pushI button 263 and momentarily depresses it every time that the door is opened or closed, the cam surface being so designed as to release the push button upon continued opening or closing movements of the door. The contact controlled by the switch button 268 is shown at 399 in Figure '7.

In the explanation given at the beginning of this description, the battery was pointed out as the source of energy for furnishing the supervising current. This reference was made for simplification of the description. In reality the battery is under trickle charge, the actual current normally Supplying the supervising current to the positive line 9 being obtained directly from the power supply terminals` indicated to the right of the battery terminal. The normal path of the supervising current is from the positive terminal 2|2 of the power supply to the point 2|3 through the contact 2|@ through the successive points 245, 2|6, and 2H, through the Wire 2|8, through the contact 2|S, through the successive points 5, 6, l, and 8 and then through the external circuits back to the negative line in the manner already described. It will be noted that the contact 219 short circuits the resistance 22).

The path of the battery charging current is from the positive terminal 2i2 of the power supply to and through the successive points 213, 2 I4, 2|6, and 2H, through the contact 2|9, to and through the successive points 5, il, and 3, through the winding of the relay 2, to the positive terminal of the battery and then to the negative line.

From the foregoing description, it will be apparent that a re detecting system is provided which is completely supervised against wire breaks, battery trouble, external circuit alarm trouble, and external circuit fire alarm lamp trouble. A single general trouble alarm bell may be employed which may be readily cleared at all times for the indication of trouble in other circuits. The trouble alarm lamps will remain lighted until the trouble has been repaired and until the trouble alarm lamp switches have been returned to their normal positions, and the system is capable of indicating exactly the location of a re, either through manual balancing means, or automatic balancing means. The system provides for checking the results rendered either manually or automatically, and permits the checking of the restoration of the thermostat that has functioned since the system cannot be returned to its normal condition unless the thermostat is restored. Variations in the resistance of the external circuits due to variations in wiring can be easily compensated for and the apparatus is capable of being arranged in a single cabinet with an appropriate door switch so that the sounding of the fire alarm bells can be stopped by the opening of the cabinet door and so that the fire must be attended to and the thermostat replaced before the cabinet door can be closed again without the repetition of the iire signal. In the event that the system is not properly reset, the closing of the cabinet door can be made to operate a resetting switch, as already hereinabove described in conjunction with Figures 6, 7 and 8.

While the invention has been described with specific reference to the accompanying drawings, it is not to be limited, save as defined in the appended claims.

I claim as my invention:

1. In combination, a plurality of circuits, current changing means in each circuit, a plurality of electro-responsive indicators corresponding respectively to the plurality of circuits, means connecting said indicators in a series circuit and including switch means, trouble indicating means associated with said series circuit and operated on failure of current therein; and means, including electro-responsive means individual to each of the plurality of circuits and a common means for operating the switch means of the series indicator circuit, for breaking the series circuit and energizing a single indicator upon operation of the current changing means of the corresponding circuit.

2. In combination, a plurality of circuits, current changing means in each circuit, a plurality of electro-responsive indicators corresponding respectively to the plurality of circuits, trouble indicating means, means in each circuit operated on failure of current therein to operate the trouble indicating means, means connecting said indicators in a series circuit and including switch means, means in said series circuit operated on failure of current therein to operate the trouble indicating means; and means, including electroresponsive means individual to each of the plurality of circuits and a common means for operating the switch means of the series indicator circuit, for breaking the series circuit and energizing a single indicator upon operation of the current changing means of the corresponding circuit.

3. In combination, a plurality of circuits, current changing means in each circuit, a plurality of electro-responsive indicators corresponding respectively to the plurality of circuits, means connecting said indicators in a series circuit and including switch means, trouble indicating means associated with said series circuit and operated on failure of current therein; means, including electro-responsive means individual to each of the plurality or circuits and a common means for operating the switch means of the series indicator circuit, for breaking the series circuit and connecting the indicators for parallel operation; and means to complete the parallel circuit of a single indicator upon operation of the current changing means of the corresponding circuit.

HARRY CAMPBELL GRANT, JR.

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