US797907A - Fire-alarm system. - Google Patents

Fire-alarm system. Download PDF

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US797907A
US797907A US21000404A US1904210004A US797907A US 797907 A US797907 A US 797907A US 21000404 A US21000404 A US 21000404A US 1904210004 A US1904210004 A US 1904210004A US 797907 A US797907 A US 797907A
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circuit
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alarm
switch
magnet
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Judson Mcfell
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    • GPHYSICS
    • G08SIGNALLING
    • G08BSIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B25/00Alarm systems in which the location of the alarm condition is signalled to a central station, e.g. fire or police telegraphic systems

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  • My invention relates to improvements in fire-alarm systems, and has for its primary objcct to provide a system having the working characteristics of an open-circuit system, but wherein the lines are subject to constant test.
  • a further object of my invention is to generally improve the arrangement of fire-alarm systems of the character described.
  • 1 provide at the central station a source of current-supply A of any suitable character, such as a set of secondary batteries, and from said source of supply extend amain or alarm circuit, which may be traced by wire 1 to one of the blade-posts 2 of a four-pole double-throw switch B, to one side of which the blades are thrown to connect the batteries to the main line and the other side whereof is connected for charging the battery.
  • the corresponding contact 3 on the first said side of the switch B is connected by wire 4: with one terminal of an electromechanical gong 5 of any well-known or preferred construction, from the other terminal of which extends wire 6, connected to one of the three-line terminals of a double-pen register 7 of any wellknown or preferred construction.
  • alarm-boxes are of any preferred construction wherein the make and break pens or contacts are normally positioned out of contact to be moved into intermittent or signal-transmitting contact when the box is actuated.
  • the circuit is looped back to the central station and may be traced by wire 11, form'ingone side of theloop, to one terminal of an electromagnetic member 12 of a central-station test device and from the other terminal of said electromagnet 12 by wire 18, forming the other side of the'loop, to the remaining terminal of the first box to which the wire 8 was directly connected. Thence the circuit extends through a series of loops 14 of unbroken continuity connecting the remaining terminals of the boxes 10 and from the last box through a wire 15, extending to the switch-contact 16, paired with the contact 3. From the corresponding blade-post 17 of the switch B extends wire 18, which is directconnected to the negative terminal of the source of current-supply A.
  • wire 8 In the present illustration from the third terminal of thedouble-pen register 7 extends wire 8, connected with a series of loops 9, extending in unbroken continuity along one side of the alarm-boxes 10, connected to one terminal of each of said boxes, thence by wire 11 to a second test-electromagnet 12 upon the, board, and back by wires 13, loops 14, and wire 15, in arrangement duplicating that of the circuit first described, to a contact 16 of a second four-pole double-throw switch B upon the board.
  • the contact 16 of switch B is directconnected with the contact 16 of switch B by wire 19, and the contact 3 in pair with contact 16 is connected to contact 3 of switch B by wire 20.
  • the corresponding blade-posts 17 and 2 of switch B are connected by wires 18 and 1 with the respective negative and positive terminals of a second source of current-supply A. It will thus be seen that either of the sources of supply A or A, or both, may be connected to the parallel alarmcircuits to supply current thereto.
  • test-magnets tact-point 22 nected by wire 29 to one terminal of a bell or are operated, and a signal indicative of the number of the actuated box is received at the central station in a manner well understood in the art.
  • each of the test-magnets 12 is a circuit-closing member controlled by such magnet and adapted to open or close a local test-circuit, accordingly as the magnet is energized or denergized.
  • 21 indicates an armature associated with a magnet 12, arranged when attracted by the magnet 12 to open contact between and when rev leased by the magnet to close contact between two points 22 and 23, forming part of a circuit which I will now describe.
  • From the'post 2 of the switch B extends wire 24, which is connected to a third post 25 of the four-pole switch B, whose corresponding contact 26 is normally connected by wire 27 through one side of a single-throw circuitbreaking switch C and by wire 28 to the con-
  • the other contact 23 is conother alarm D, from the remaining terminal of which extends a wire 30, connected through 1 the other side of the switch C to the last contact-post 31 ,on the one side of switch B.
  • the corresponding post 32 of said switch is connected by wire 33 with the post 17 of the switch B.
  • the magnet 12 is provided with an armature 21, whose contacts 22 and 23 are connected in circuit exactly corresponding to that last described, the parts whereof are indicated'by like characters of reference differentiated by the exponent numeral prime,
  • the main circuit under the conditions re- .ferred to may be traced from battery A by ,wire 1, post 2, the switch-blade contact 3, and
  • testcircuits are connected in parallel as follows: From battery A extends wire 1 to post 2.
  • the other branch ofthe circuit starting from the post 26 includes tie-wire 35, contact 26, the bell-circuit 27, blade of switch 0', 28, 23, 22, 29, D, and 30' to the post 31 by tiewire 34 to contact 31, thence returning to the battery A, as before described. If the condition of switches B and B be reversed,
  • the main circuits receive current from battery A, while the test-circuits are connected with battery A. 1
  • the battery A supplies current by wire 1 and the blade 2 to the contact 3, which is connected by tie-wire 20 to the contact 3, forming part of the main circuit above described, the return from the main circuit. being completed from the contacts 16 and 16, which are connected by wire 19, through the blade of switch B, by wire 18, to the negative terminal of the battery, the remaining portions of the respective main circuits being as before described.
  • test circuit receives current from battery A, the connected contacts 26 and 26 forming part of said circuit, being electrically connected with the positive terminal of the battery A by wire 1 and wire 24, the post 25 of switch B, and the associated blade of said switch, while the connected posts 31 and 31, tied together by wire 34 and constituting, as above described, part of the test-circuit, are electrically connected with the negative terminal of the battery by wire 18, post 17, wire 33, post 32 of the switch B, and the associated blade which makes contact with the part 31.
  • I also prefer to provide at the central station voltmeter-s V and V, arranged to be connected with the respective alarm-circuits,-
  • I also prefer to provide on the switchboard a means for connecting either or both of said batteries with the charging-circuit.
  • I provide a signal-throw switch G, two of the contact members whereof are connected to the positive and negative wires of a charging-line circuit and the remaining terminals whereof are connected in a circuit which I will now trace.
  • switch G eX From one of the terminals of switch G eX tends wire 42, tapped to a wire 43, connecting two contacts 4A and 44: of the switches B and B, respectively, arranged for coaction with the blades carried by the posts 2 and 2.
  • contacts L5 and 45 Arranged for coaction with the blades carried by the posts 17 and 17 are contacts L5 and 45, connected by wire 46, to which is tapped wire 4:7, havinga loop 48 between the wires whereof are bridged suitable electric lamps L or other resistance devices and from the loop 48 extending by wire 49 back to the remaining terminal of the switch G.
  • a normally closed circuit including therein a high-resistance magnet and signal-responsive means adapted to work on closed circuits, said signal-responsive means being non-responsive to the normal current-flow in the circuit and responsive to the current-flow therethrough when the magnet is short-circuited, and a source of current-supply for said circuit, a plurality of normally open signal-transmitting means each adapted to transmit a characteristic distinguishable signal, and each adapted and arranged to short-circuit the resistance-magnet when actuated, and means associated with said magnet for indicating when it is short-circuited-.
  • a normally closed circuit including a higl resistance magnet and signal responsive means located at'a supervising-station, said signal responsive means being adapted to work on a closed circuit and being non-responsive to the normal current-flow in the circuit and responsive to the currentflow therethrough when the magnet is short-circuited, means for supplying current to said circuit, a plurality of normally open signaltransmitting means adapted to transmitdifferent distinguishable signals and each adapted and arranged to short-circuit the resistancemagnet when actuated, a normally open testcircuit including at the su iiervising-station a signaling device, and means for closing said test-circuit controlled by the high-resistance magnet and adapted to close said circuit when the magnet is short-circuited.
  • a normally closed main circuit including a source of current-supply and, at a supervisory station, a high-resistance magnet and signalresponsive means, non-responsive to the nor- -mal current-flow in the circuit and responsive to the current-flow therethrough when the magnet is short-circuited
  • a plurality of normally open signal-transmitting means adapted and arranged to transmit distinguishable predetermined signals and arranged to shortcircuit the resistance-magnet when actuated
  • a normally open local shunt-circuit from the alarm -circuit including at the supervisory station a signal device, and means for closing said shunt controlled by the resistancemagnet.
  • a central-energy fire-alarm system comprising a central source of current-supply, a plurality of normally closed parallel alarm-circuits each including a high-resistance magnet, signal-responsive means operatively associated with said alarm-circuits, a plurality of normally open signal-transmitting means associated with each alarm-circuit each adapted to transmit a distinguishable signal and adapted and arranged when actuated to short-circuit the resistance-magnet of said circuit, a mormally open test-circuit associated with each alarm-circuit, and a test-circuit-closing means controlled by the high-resistance magnet of said alarm-circuit, adapted to close the test-circuit When the magnet is short-circuited or deenergized.
  • acentral-energy fire-alarm system the combination of acentral source of current-supply, parallel alarm-circuits, normally closed alarm-circuits connected in parallel With said source of supply, and each including a highresistance magnet, signal-responsive means operatively associated With said alarm-circuits, a plurality of normally open signaltransmitting means for each alarmcircuit each adapted to transmit a distinguishable signal and adapted and arranged When actuated to short-circuit the resistance-magnet of said circuit, local test-circuits corresponding With the alarm-circuit connected in parallel to the central battery, and a circuit-closing means for each of said test-circuits controlled by the high-resistance magnet of the corresponding alarm-circuit.
  • a normally closed circuit including a high resistance
  • a plurality of normally open signaltransmitters each adapted to transmit a predetermined distinguishable signal and adapted and arranged when actuated to short-circuit the resistance
  • a signal-responsive device in the closed circuit not responsive to the normal current-flow through the circuit but operative by the flow When the resistance is short-circuited, and a source of current-supply for said circuit.
  • cuit including an alarm device and a circuitcontrolling instrumentality controlled by the electromagnet of the corresponding alarmcircuit, and means for connecting the alarmcircuits in parallel to one source of currentsupply and the test-circuits to the other source of supply.
  • a fire-alarm system the combination of two sources of current-supply, a plurality of closed alarm-circuits each including an electromagnet, a test-circuit associated with each alarm-circuit including an alarm device, and a circuit-controlling instrumentality controlled by the electromagnet of the corresponding alarm-circuit, and reversible means for connecting the alarm-circuit in parallel to either source of current-supply and the test-circuit to the other source of current-supply.

Description

PATENTED AUG. 22, 1905.
J. MQFELL.
FIRE ALARM SYSTEM.
APPLICATION FILED MAY27,1904.
ANDREW a. (mum co" PNDTO-LITHOGRAPMERS, wAsmucrofl, n. a
UNITED STATES PATENT oFFIoE.
FIRE-ALARM SYSTEM.
Specification of Letters Patent.
Patented Aug. 22, 1905.
Application filed May 27, 1904- Serial No. 210,004.
To II/N/ whom it may concern:
Beit known that I, J UDSON MoFnLL, of Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Fire-Alarm Systems; and I hereby declare that the following is a full, clear, and exact description thereof, reference being had to the accompanying drawing, which forms part of this specification.
My invention relates to improvements in fire-alarm systems, and has for its primary objcct to provide a system having the working characteristics of an open-circuit system, but wherein the lines are subject to constant test.
A further object of my invention is to generally improve the arrangement of fire-alarm systems of the character described.
To these and other ends, which will become apparent to those skilled in the art from the following description, my invention consists in the features of arrangement and combinations of parts hereinafter more fully set forth, and specified in the claims.
In the drawing I have illustrated the embodiment of my invention in a single figure diagrammatically representing the apparatus employed associated with proper electric circuits.
Referring now to the drawing, it will be seen that 1 provide at the central station a source of current-supply A of any suitable character, such as a set of secondary batteries, and from said source of supply extend amain or alarm circuit, which may be traced by wire 1 to one of the blade-posts 2 of a four-pole double-throw switch B, to one side of which the blades are thrown to connect the batteries to the main line and the other side whereof is connected for charging the battery. The corresponding contact 3 on the first said side of the switch B is connected by wire 4: with one terminal of an electromechanical gong 5 of any well-known or preferred construction, from the other terminal of which extends wire 6, connected to one of the three-line terminals of a double-pen register 7 of any wellknown or preferred construction. From one of the remaining binding-posts of said register 7 extends wire 8, which is connected in a series of loops 9 of unbroken continuity to one binding-post of each of the alarm-boxes 10. These alarm-boxes are of any preferred construction wherein the make and break pens or contacts are normally positioned out of contact to be moved into intermittent or signal-transmitting contact when the box is actuated.
From the last of the boxes 10 the circuit is looped back to the central station and may be traced by wire 11, form'ingone side of theloop, to one terminal of an electromagnetic member 12 of a central-station test device and from the other terminal of said electromagnet 12 by wire 18, forming the other side of the'loop, to the remaining terminal of the first box to which the wire 8 was directly connected. Thence the circuit extends through a series of loops 14 of unbroken continuity connecting the remaining terminals of the boxes 10 and from the last box through a wire 15, extending to the switch-contact 16, paired with the contact 3. From the corresponding blade-post 17 of the switch B extends wire 18, which is directconnected to the negative terminal of the source of current-supply A.
I have shown my system as comprising two main or alarm circuits connected in parallel to derive current from the central source of supply, though obviously any number of alarm-circuits might be employed by simple extension of the system and multiplication of the mechanical devices.
In the present illustration from the third terminal of thedouble-pen register 7 extends wire 8, connected with a series of loops 9, extending in unbroken continuity along one side of the alarm-boxes 10, connected to one terminal of each of said boxes, thence by wire 11 to a second test-electromagnet 12 upon the, board, and back by wires 13, loops 14, and wire 15, in arrangement duplicating that of the circuit first described, to a contact 16 of a second four-pole double-throw switch B upon the board.
While I have shown but a single gong and register for the two alarm-circuits, obviously separate gongs and registers might be employed. The contact 16 of switch B is directconnected with the contact 16 of switch B by wire 19, and the contact 3 in pair with contact 16 is connected to contact 3 of switch B by wire 20. The corresponding blade-posts 17 and 2 of switch B are connected by wires 18 and 1 with the respective negative and positive terminals of a second source of current-supply A. It will thus be seen that either of the sources of supply A or A, or both, may be connected to the parallel alarmcircuits to supply current thereto.
It will be understood that the test-magnets tact-point 22. nected by wire 29 to one terminal of a bell or are operated, and a signal indicative of the number of the actuated box is received at the central station in a manner well understood in the art.
Associated with each of the test-magnets 12 is a circuit-closing member controlled by such magnet and adapted to open or close a local test-circuit, accordingly as the magnet is energized or denergized. Specifically, 21 indicates an armature associated with a magnet 12, arranged when attracted by the magnet 12 to open contact between and when rev leased by the magnet to close contact between two points 22 and 23, forming part of a circuit which I will now describe.
From the'post 2 of the switch B extends wire 24, which is connected to a third post 25 of the four-pole switch B, whose corresponding contact 26 is normally connected by wire 27 through one side of a single-throw circuitbreaking switch C and by wire 28 to the con- The other contact 23 is conother alarm D, from the remaining terminal of which extends a wire 30, connected through 1 the other side of the switch C to the last contact-post 31 ,on the one side of switch B. The corresponding post 32 of said switch is connected by wire 33 with the post 17 of the switch B.
The magnet 12 is provided with an armature 21, whose contacts 22 and 23 are connected in circuit exactly corresponding to that last described, the parts whereof are indicated'by like characters of reference differentiated by the exponent numeral prime,
- said circuit being connected with the switchposts 17 and 2 of the switch B. Furthermore,
contacts 31 and 31 of the switches B and B are connected together by wire 34, while the contacts 26 and 26 are connected by wire 35. Thus it will be seen that if the switch B be thrown to closed position relative to the contacts heretofore described and the switch B be opened the parallel main-line circuits will receive current from the battery A, while both test-circuits, including the bells D and D, respectively, will receive current from the other battery A.
The main circuit under the conditions re- .ferred to may be traced from battery A by ,wire 1, post 2, the switch-blade contact 3, and
parts 4, 5, and 6 to the register 7, where the circuit divides, one branch extending through the parts 8 9 11-12 1314 15, contact 16, switchblade, and post 17, to the return-wire 18, leading back to battery A, and the other branch taking its course through parts 8 9 11 12 13 14 15 16 and the tie-wire 19 to the post 16 of the switch B, whence return is had from the battery, as before described. The testcircuits are connected in parallel as follows: From battery A extends wire 1 to post 2. of the switch B, thence by wire 24 to the post 25 of switch B, and through the switch-blade to the contact 26, where the circuit divides, one branch taking a path through parts 27, a blade of the switch B 28 22, the armature 21, (if down upon the contacts 22 and 23,) the remaining contact 23, wire 29, bell D, wire 30, contact 31, the upper switchblade of the switch B, post 32, wire 33, post 17, and wire 18 to the negative terminal of the battery A. The other branch ofthe circuit starting from the post 26 includes tie-wire 35, contact 26, the bell-circuit 27, blade of switch 0', 28, 23, 22, 29, D, and 30' to the post 31 by tiewire 34 to contact 31, thence returning to the battery A, as before described. If the condition of switches B and B be reversed,
, the main circuits receive current from battery A, while the test-circuits are connected with battery A. 1
Under the last-mentioned conditions the battery A supplies current by wire 1 and the blade 2 to the contact 3, which is connected by tie-wire 20 to the contact 3, forming part of the main circuit above described, the return from the main circuit. being completed from the contacts 16 and 16, which are connected by wire 19, through the blade of switch B, by wire 18, to the negative terminal of the battery, the remaining portions of the respective main circuits being as before described. Under these conditions also the test circuit receives current from battery A, the connected contacts 26 and 26 forming part of said circuit, being electrically connected with the positive terminal of the battery A by wire 1 and wire 24, the post 25 of switch B, and the associated blade of said switch, while the connected posts 31 and 31, tied together by wire 34 and constituting, as above described, part of the test-circuit, are electrically connected with the negative terminal of the battery by wire 18, post 17, wire 33, post 32 of the switch B, and the associated blade which makes contact with the part 31.
It will now be apparent that if trouble should occur upon the main line which would deenergize either magnet 12 or 12-such, for instance, as the breaking of the line-circuit the armature of such deenergized magnet will drop, closing the corresponding test-circuit through the alarm D, and thereby giving a trouble-signal to the central-station operator.
I also prefer to provide at the central station voltmeter-s V and V, arranged to be connected with the respective alarm-circuits,-
either within the loop of said main circuit adjacent the source of current-supply therefor.
' F, one pair of contacts whereof are connected by wires 38 and 39, respectively, to wires 33 and 24, which, it will be remembered, are di- 'rect-connected to the switch-posts 17 and 2,
respectively, constituting part o'f-the main circuit. The remaining terminals of the switch F are connected by wires 40 and 4:1, respectively, with wires 11 and 18, so that when the switch is thrown to one side or the other the voltmeter shows the condition of the main line at the end of the loop or near the terminals of the source of supply. v
In case secondary or storage batteries are used as a source of current-supply I also prefer to provide on the switchboard a means for connecting either or both of said batteries with the charging-circuit. To this end I provide a signal-throw switch G, two of the contact members whereof are connected to the positive and negative wires of a charging-line circuit and the remaining terminals whereof are connected in a circuit which I will now trace.
From one of the terminals of switch G eX tends wire 42, tapped to a wire 43, connecting two contacts 4A and 44: of the switches B and B, respectively, arranged for coaction with the blades carried by the posts 2 and 2. Arranged for coaction with the blades carried by the posts 17 and 17 are contacts L5 and 45, connected by wire 46, to which is tapped wire 4:7, havinga loop 48 between the wires whereof are bridged suitable electric lamps L or other resistance devices and from the loop 48 extending by wire 49 back to the remaining terminal of the switch G. It will be apparent that when the switch Gr is closed the blades of either of the switches B or B may be thrown to connect the corresponding battery with the charging-circuit, and it will be apparent that by'alternately charging and discharging the batteries the main-line circuit may be constantly maintained in operative condition.
While I have herein described my system as comprising two parallel alarm-circuits and two sets of like devices each associated in like manner with their respective alarm-circuits, it will be apparent that certain of the features of my invention are independent of the duplication of the circuits and devices and may be applied with advantage to a single-circuit system.
It will also be apparent that numerous changes might be made in the specific apparatus employed in the embodiment of my invention without departing from the spirit and scope thereof.
WVhat I claim, and desire to secure by Letters Patent of the United States, is-
1. In a fire-alarm system, the combination of a normally closed circuit including therein a high-resistance magnet and signal-responsive means adapted to work on closed circuits, said signal-responsive means being non-responsive to the normal current-flow in the circuit and responsive to the current-flow therethrough when the magnet is short-circuited, and a source of current-supply for said circuit, a plurality of normally open signal-transmitting means each adapted to transmit a characteristic distinguishable signal, and each adapted and arranged to short-circuit the resistance-magnet when actuated, and means associated with said magnet for indicating when it is short-circuited-.
2. In a fire-alarm system, the combinatio of a normally closed circuit including a higl resistance magnet and signal responsive means located at'a supervising-station, said signal responsive means being adapted to work on a closed circuit and being non-responsive to the normal current-flow in the circuit and responsive to the currentflow therethrough when the magnet is short-circuited, means for supplying current to said circuit, a plurality of normally open signaltransmitting means adapted to transmitdifferent distinguishable signals and each adapted and arranged to short-circuit the resistancemagnet when actuated, a normally open testcircuit including at the su iiervising-station a signaling device, and means for closing said test-circuit controlled by the high-resistance magnet and adapted to close said circuit when the magnet is short-circuited.
3. In a fire-alarm system, the combination of a normally closed main circuit including a source of current-supply and, at a supervisory station, a high-resistance magnet and signalresponsive means, non-responsive to the nor- -mal current-flow in the circuit and responsive to the current-flow therethrough when the magnet is short-circuited, a plurality of normally open signal-transmitting means adapted and arranged to transmit distinguishable predetermined signals and arranged to shortcircuit the resistance-magnet when actuated, a normally open local shunt-circuit from the alarm -circuit including at the supervisory station a signal device, and means for closing said shunt controlled by the resistancemagnet.
4. A central-energy fire-alarm system, comprising a central source of current-supply, a plurality of normally closed parallel alarm-circuits each including a high-resistance magnet, signal-responsive means operatively associated with said alarm-circuits, a plurality of normally open signal-transmitting means associated with each alarm-circuit each adapted to transmit a distinguishable signal and adapted and arranged when actuated to short-circuit the resistance-magnet of said circuit, a mormally open test-circuit associated with each alarm-circuit, and a test-circuit-closing means controlled by the high-resistance magnet of said alarm-circuit, adapted to close the test-circuit When the magnet is short-circuited or deenergized.
5. In a central-energy fire-alarm system, the combination of acentral source of current-supply, parallel alarm-circuits, normally closed alarm-circuits connected in parallel With said source of supply, and each including a highresistance magnet, signal-responsive means operatively associated With said alarm-circuits, a plurality of normally open signaltransmitting means for each alarmcircuit each adapted to transmit a distinguishable signal and adapted and arranged When actuated to short-circuit the resistance-magnet of said circuit, local test-circuits corresponding With the alarm-circuit connected in parallel to the central battery, and a circuit-closing means for each of said test-circuits controlled by the high-resistance magnet of the corresponding alarm-circuit.
6. In a fire-alarm system, the combination of a normally closed circuit including a high resistance, a plurality of normally open signaltransmitters each adapted to transmit a predetermined distinguishable signal and adapted and arranged when actuated to short-circuit the resistance, a signal-responsive device in the closed circuit not responsive to the normal current-flow through the circuit but operative by the flow When the resistance is short-circuited, and a source of current-supply for said circuit.
7. In a fire-alarm system, the combination of tWo sources of current-supply, a plurality of closed parallel alarm-circuits, each includa test-circuit associated With each alarm-cir-.
cuit including an alarm device and a circuitcontrolling instrumentality controlled by the electromagnet of the corresponding alarmcircuit, and means for connecting the alarmcircuits in parallel to one source of currentsupply and the test-circuits to the other source of supply.
8. In a fire-alarm system, the combination of two sources of current-supply, a plurality of closed alarm-circuits each including an electromagnet, a test-circuit associated with each alarm-circuit including an alarm device, and a circuit-controlling instrumentality controlled by the electromagnet of the corresponding alarm-circuit, and reversible means for connecting the alarm-circuit in parallel to either source of current-supply and the test-circuit to the other source of current-supply.
In testimony that I claim the foregoing as my oWn I aflix my signature in presence of two Witnesses.
J UDSON MoFELL. In presence of- GEO. T. MAY, J r., MARY F. ALLEN.
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