US2247251A - Burglar alarm - Google Patents

Description

Jun; 24, 1941. c. E. POTTER BURGLAR ALARM Filed Dec 31, 1957 5 Sheets-Sheet 2 INVENTOR. CHA PL ES E. POT TER BY HIS Arromvsm.

June 24, 1941. c. E. POTTER BURGLAR ALARM Filed Dec. 31', 1937 5 Sheets-Sheet 3 MW J 5 W June 24, 1941. c. PQTTER 2,247,251

BURGLAR ALARM Filed Dec. 31, 1957 5 Sheets-Sheet 4 June 24, 1941.

c. E. POTTER BURGLAR ALARM 5 Sheet-Sheet 5 Filed Dec. 31, 1937 MOTOR FULLY WOO/V0 IIWENTO/P CHARLES E. POTTER H S ATTORNEYS.

Patented June 24, 1941 UNITED STATES ()FFICE This invention relates to burglar alarm systems and particularly to that type of system which has a central station and a transmitting station, and relates especially to the apparatus and circuits at the transmitting station.

An object of this invention is to provide apparatus and circuits which will be efficient in service for transmitting signals from a station to be protected to a central or observation station.

Other and specific objects of the invention will be apparent from the following detail description taken in connection with the accompanying drawings, while the invention,v oomprises the parts and their combinations especially pointed out in the appended claims.

Fig. 1 is a perspective view of a cabinet enclosing apparatus hereinafter described and constituting a part of this invention;

Fig. 2 is a fragmentary view of the cabinet shown in Fig. 1 with a door open;

Fig. 3 is a diagram of the circuits at the transmitting station;

Fig. 4 is an elevation showing apparatus embodying the invention;

Fig. 5 is a rear elevation of a transmitting instrument;

Fig. 6 is a front elevation partly in section;

Fig. '7 is a side elevation;

Fig. 8 is a side elevation opposite that of Fig. 7;

Fig. 9 is a detail showing a code wheel, and Figs. 10, 11 and 12 are diagrams showing the position of certain cams and. their switches during different phases of their cycle.

In systems of this character one or more loop circuits are provided for protecting the premises, with means so arranged that when one of such circuits is broken by unauthorized entry into the premises, the breaking of a loop circuit will cause the operation of the mechanism to rotate a code wheel I and thereby transmit a signal to the central station. Such a mechanism, as will be understood from the detail description hereinafter given, will include a rotating cam 2 which controls certain switches. The mechanism is propelled by a spring motor and the cam 2 assumes a position in accordance with the condition of the motor. A circuit 3, 4, is connected between the transmitting station and the control station. A code wheel I is arranged to intermittently break the circuit 3, 4 and also to intermittently ground the line 3. Means for breaking and grounding the circuit 3, 4 includes brushes 5 and 5 conductively cQnnBGted with the wire 3. The brush 5 carries a point I normally in contact with a stationary member 8 connected to the line 4. The brush 6 carries a point 9 which may contact a member IIl connected to a ground wire II. As the code wheel I is rotated its projections I2 will break the contact between the points I and 8, to open the circuit 3, 4 and to make contact between the points 9 and In to ground the line 3. It will be understood that means are provided at the central station for maintaining a constant current through the circuit 3, 4.

Means are also provided at the central station for supplying to the line 3, 4 an alternating current of audio frequency, while means are provided at the transmitting station for receiving a signal which is transmitted from the central station by means of the current of audio frequency. The circuit at the transmitting station to receive such a signal is as followsz-From theline 3 through the wire 92, through a manually operable switch 93, through a wire 94 to a buzzer 95, to a condenser 99, through a conductor 91 to a contact 98, through a brush 99, through a wire Hill to the ground wire II,

For the present it may be understood that when the spring motor, driving the cam 2, is not wound the brush 99 will lie away from the contact 98, but when the spring motor is wound and ready for operation, as will be described later in detail, the brush 99 will close on the contact 98. It may be understood that before such a contact is made the mechanism has caused the code wheel I to give a predetermined signal to the central station. such a signal the operator at the central station will connect the line 3 with the source of alternating current of audio frequency to operate the buzzer 95. From subsequent description it will be understood that when the mechanism is in such condition that the brush 99 touches the contact 98 the apparatus is in condition for operation by relays under control of the loop or protection circuits and therefore a receipt of a buzzer signal is proof at the transmitting station that the entire system is in proper order.

In my application Serial No. 182,687 filed on even date herewith, I have illustrated and described in detail, and claimed the circuits at the central station and in combination the signal receiving circuit at the transmitting station above described.

For convenience binding posts or terminals IIH, I92, I93, I94, I05, I06, I01, I98, I09 and H9 Upon receiving dropping its armature I34;

are provided. Line 3 is connected to terminal IOI, line 4 to I02; ground wire 4 to I03; an alarm circuit III, I I2 which includes a bell II3, to I04 and I05; a power circuit II4, II5, supplied by a battery IIO, to I06 and I01; the end of a loo-p protection circuit II1 to I01 and I08; and the ends of a second loop protection circuit II8 to I09 and H0.

The alarm circuit III, II2 may lead a considerable distance from the control apparatus so that the bell II3 may be placed at a point to give a public alarm.

The loop circuits H1 and H8 will be arranged about openings in a premises so that an unauthorized entry will cause one of the circuits to be broken, thereby causing operation of the mechanism, in a manner and by means hereinafter described, to rotate the code wheel for transmitting a signal to the central or observation station and also to energize the alarm circuit III, II2 for giving a public alarm.

A feed? circuit line for energizing the loop circuits and the relays is as follows: from the terminal I06 (connected to the battery IIG by the 'wire 4) through awire IIO, through a brush'120 (operated by the cam 2),'and a'contactiIZI, to a wire I22.

When" the mechanism is in condition to operate responsive tothe loop'circuits the brush I20 will'beclosed on the contact 'I2I; otherwise the circuit will be open at this point. In order to test the loop circuits before the mechanism is wound, a push button switch I23 is provided across" the lines I19 and I22, and in parallel with the cam operated switch I20, I2 I.

The protection circuit, including the loops H1 and I I 8, has follows? from the wire I22, which isconne'ct'ed through a feed line as above described to one side of the battery II 6, through a wire I 24, a tamper switch I25, 21; low-ohmic relay (e. g. 85 ohms)" I26, a wire I21 to the terminal IIO, through the loop II8 to th terminal I09, through a wire I28 to a high-ohmic relay (e. g. 1,000 ohms) I29, through a wire I30 to a milliammeter I3I,' through a. wire I32 to the terminal I03, through. the loop II 1' to the terminal I01 and then through the wire II5, completing the circuit to the battery H6.

The relays I25 and I29 have their armatures I33'and I34 so' arranged as to complete a circuit to an operating relay I35, to trip and permit th operation of the spring motor for rotating the code wheel I, either by the relay I23 pulling up its armature. I33 'or the relay I25 Therefore, if there is a break in neither of the loops H1, H0, or if the tamper switch "I25 opens, or if there is ashunt' between the'loops H1 and H8, the relay I20 will be deenergized permitting its armature: to drop; contacting a point I36'to complete a circuit as'followsz from wire I22 (connected byiia feed line above described to one side of theibattery. I'Ifi) through a wire I31, through thearmature I34 to point I36, through; a wire I38 to the relay .I'35,'; through a wire I39 to the terminal I101 and then'through the wire II 5, completing the circuit to the battery H6.

in the event of a shunt in the system, which may be insufiicientto-operate the relay I29, the increasedflow through the relay I26 will cause it'to drawup its armature I33 to make contact with a point I40; closing a circuit between the wire. I22,and the wire I38; the wire I22 being connected by a Wire I41 to the armature I33,

and the point I40 being connected by a wire I42 to the wire I30.

The relay I35 includes an armature I43 which has a projection or detent I44, adapted when down to engage and stop the mechanism or spring motor, and when up to release the mechanism, permitting it to operate the code Wheel I to transmit a signal. It is arranged also to contact a point I45 to complete a holding circuit for the relay. The circuit has a cam operated switch which includes a contact I45, connected by a wire I41 to the relay I35, and a brush I48, connected by a wire I49 to the armature I43. The brush I48 is operated by a cam I50 on the same shaft I5I as the cam 2. The cam switch 7 is required to avoid completing the circuit during the initial operation of the code wheel. It is so arranged as'to close at the time the detent I44 drops to stop the mechanism at the close of the initial operation of the code Wheel. Therefore the cam switch I40, I40 is closed when the mechanism is properly set for its protective operation, and the holding circuit will be closed when th relay draws up. The holding circuit is as follows: from the point I45 on the feed line I22, through the-armature I43, wire I49, brush I48, contact I43 and wire I41, to the relay I35, and thence through thewire I39 to'the battery as previously described. 7

While a mechanical latch for the detent I44 has been provided, the-latch is slow-acting, and. the holding circuit for the relay I35 prevents the armature fromdropping if the loop circuits are-broken only momentaril The alarm or bell circuit III, H2 is connected by a switch operated by thecam 2 and including the brush I20 and a contact I52. The arrangement is such that the brush I20 closes on the contact as soon as the high surface on the cam rotates away from the brush and the circuit remains closed until opened by a manually operable switch I52 The complet alarm circuit is as follows: from one terminal of the battery H6, through the wire II4 tothe terminal I05, through wire I19, brush I20,con-

tact I52, wire I52 switch I'53 wire I53 to terminal I04, thence through bell circuit III, H3, H2, to terminal I05, through wire I54 to terminal I01 and through wire 5' to the opposite pole of the battery H5.

Use of the alarm circuit is optional and it may be included oromitted without aifecting the operation of the remaining parts. Hence, it is shown only on the. diagram Fig. 2 and not on the remaining figures. It will be understood, however, that the switch I52 may be located conveniently and safely on the panel I58 where it is operable only upon opening the door I51.

The terminals IOI to II 0, the circuits, mechanism and the devices shown in Fig. 3 above the terminals, the battery II5 and'its connect: ing circuit II4, II5are' enclosed within a cabinet I (Figs. 1 and 2) which has a main door or cover I 55 and a panel door I51. The door I51 provides access to .a panel, I50 upon which is mounted the transmitting mechanism, relays and other parts, as best shownin Fig. 4. The door I51 is secured by a dog I59 which when overthrown contacts and moves a lever I60 to turn a cam I6I closing the switch 93. The shaft I5I of the spring motorand transmitting mechanism extends through the panel I58 and carries a crosshead or key I62 for windingthe motor. The door I56 is secured by a bolt I50 reached through the opening of the panel door I51.

When the system is to be placed in operation preparatory to closing for the night, the door I51 is opened, the mechanism is wound by the key I62, the door is closed and the dog I59 is overthrown to depress the lever I60. Thereby the spring motor is caused 'to operate in such a manner as to turn the code wheel I a single revolution, giving the central station a signal that the premises are about to be closed. The switch 93 is set by depressing the lever I60 so that the signal receiving circuit, including the buzzer 95 is placed in condition for receiving a signal. The milliammeter I3I, visible through a window in the door I56, of'the cabinet, will indicate that current is flowing through theloop circuits and upon sounding of the buzzer 95 the person in charge of the premises will know that the entire system is in working condition. Then a door key, by which the dog I59 is depressed, will be released and the switch 93 will be opened.

The signal transmitting mechanism is mounted on the panel I58 and includes a pair of frame plates I63, I64 upon which the parts are mounted or journalled. The mechanism comprises in part a spring motor which includes a main shaft I5I to which is connected cams 2 and I50 and upon which is mounted a gear I65, which has a pawl and ratchet connection with a shaft whereby it will be turned when the shaft is operated by a spring I66 but will remain stationary when the shaft I5I is turned for winding.

The gear I65 drives a pinion I61 secured to a shaft I68 on the outer end of which is mounted the code wheell! A gearI69 is secured to the shaft I68 and drives a pinion I on a'shaft I1I, to which is secured an escapement wheel I12. An escapement balance I13 has a point I14 adapted to mesh with teeth on the escapement wheel I12 and has a hook or abutment member I15 positioned to contact the detent I44, carried on the outer end of the armature I43, by which the mechanism'is blocked when the armature is down and is tripped for operation when the armature is raised.

A latch plat I16 is pivot-ally mounted on the front plate I64 by a pin I11 and carries at its lower end, best shown in Fig. 6, an arm with a notch I18 for'receiving and holding an outwardly extending projection or arm I19 of the armature I43. The latch plate I 16 has at its'lower end, just below the notch I18, a bevelled edge I80 for engagement with the end of the arm I19 'by which it may b lifted up into position in the notch I18 to mechanically raise the armature I43. Th latch plate I16 has an open slot I8l through which projects the shaft I5I, carrying on its outer end a cross pin I82.

Means are provided for positively moving the latch plate I16 outwardly to raise and hold the armature I43 when the spring I66 is fully wound in order to give an initial revolution to the wheel I, and thereby transmit a signal to the central or observation station. This means includes a cam member 183 journalled on the outer end of the shaft I5I between the cross pin I82 and the latch plate I16. The cam I 83 has an outwardly extending pin I84 for engagement by the cross pin I82 when the spring is wound by turning the shaft I5I in a clockwise direction (Figs. 4 and 6), and the latch plate I16 has an outwardly extending pin I85 for engagement by a hook surface of the cam I33 when the spring is wound. Thus when the shaft I5I is turned in a clockwise direction, Figs. 4 and 6, to wind the spring, at the end of the operation the cross pin I82 on the shaft I5I will engage the pin I84 on the cam I83 to turn the cam for engagement with the pin I85 on the latch plate, thereby swinging the latch plate to the left (Figs. 4 and 6) so that'the bevelled surface I80 at the bottom of the latch will engage the end of the arm I19 on the armature I43 forcing it upwardly and into engagement with the notch I18,

Therefore, as soon as the spring is wound, the detent I44 will be raised tripping the mechanism and permitting it to operate under influence of the motor to turn the code wheel I a single revolution. Means are provided for releasing the latch at the end of the initial operation of the code wheel and these means include a cross pin I86 and a cam plate I81 fastened by screws I88 to the underside of the latch plate I16. Now as the shaft I5I rotates in a counter-clockwise direction (Figs. 4 and 6) and after it is moved sufiiciently to cause rotation of the code wheel I a single revolution, the pin I 86 will engage the lower point of the cam plate I81 to swing the latch plate I16 outwardly to release the arm I84, permitting the armature I43 to fall and bringing the detent I44 into engagement with the abut-- ment I15 on the escapement balance to stop the operation of the mechanism. Then the mechanism or spring motor will not operate the code wheel until the armature I43 has been lifted by the relay I35.

But as soon as the shaft I5I has been further operated but slightly in a counter-clockwise direction (Figs. 4 and 6) the pin I86 will'mo've out of engagement with the point of the cam plate I81 permitting the latch plate to move to the left under the influence of a light spring I89. Therefore, after the mechanism has been tripped by operation of the relay I35 and the detent I44 has been moved upwardly to trip the mechanism the latch plate I16 will move outwardly to latch the armature I43 in up position.

Means are provided for mechanically unlatching the mechanism at the end of the cycleand this means includes a pin I90 on the latch plate I16, positioned for engagement by an appropriat surface on the cam I83, and a pin I9I on the cam I83 for engagement by the cross pin I82,'as clearly shown in Figs. 4 and 6. Thus, at the end of the proper number of revolutions of the code wheel I the latch plate I16 will be positively moved to the right to unlatch the detent, thus giving a signal by a predetermined numberof revolutions of the code wheel.

The cam 2 is secured on and rotates with the shaft I5I. It is so constructed and arranged that the brushes 99 and I20. which are mechanically connected together, are permitted to move to the left and out of engagement with the contacts 98 and I2I when the spring motor 'is'unwound. In that condition of the mechanism the cam 2, as well as the cam I50, will assume the position as shown in Fig. 3. Therefore, when the apparatus is unwound, following the giving of a warning signal, or following the authorized opening of the premises, the supply line or-circult will be disconnected preventing unnecessary use of electricity. Then upon the initial operation of the motor to give the initial closing signal, the cam 2 and the cam I50 will operate in a counter-clockwise direction (Fig. 3) andthe high surface on the cam 2 will close the brushes 99 and I20 against the contacts 98 and I2-I rea signal. At the end of such initial operation the cam I250 willmove so. that the brush I48 will close. against the. contact I46. After the commencement: of the subsequent operation of the mechanism the cam 2 will move so as to release the. brushes 99 and. I20, but not until the latch The operation or cycle of the device includes inasequ'ence (w) Aninitial testing of the loop circuits;

("bi Winding the motor, which (c) Releases the motor mechanism causing it to turn. the code wheel I one revolution, to give a predetermined signal to the central or observation station through the lines 3, 4, and

((i) To turn the cam 2 to a position to close the loop circuits at I20, I2I and the test circuit at. 98, 9.9;

(e); Closingthe manual switch S3 in the test circuit;

(j): Receipt of. a test signal on the buzzer 05 from the central station;

(9) Release of the motor through the stick relay I35 by a defect in the loop circuits either,

(h); By ashunt, causing the relay I26 to close E33,. [40,. or

'(ii) By abreak; causing relay I29 to close I34, I36;

(ii) Accompanied by a rotation of the cam I 50; to close: immediately the holding circuit at I46 I48 for the relay I 35, and followed by (To) A mechanical latching of the detent I44 in. release position.

The following details are given in the same se quence and with the identifying letter as used above.

(a) In preparing the transmission station for operation at the close of business in the evening the first step is an initial testing of the loop cir cuits. At that timethe spring motor will be unwound because of a break of the protection loop when the premises are opened in the morning.

The position of the cams 2 and I50 will be as shown. specifically in Fig. 12. The feed line II9 from the battery IIG to the line I22 for the loop circuits H1 and H will be disconnected by the brush I20 standing away from the contact IZI, also as shownin Fig. 3, which may be followed in tracing the circuit in this description of the preliminary condition of the system. The person inic'harge of the premises will first press the button I23, to connect the loop circuits with the battery, and if the loops H1 and H8 are unbroken and in proper condition current will flow throughthese loop and will be read on the milliammeter I3I. If the milliammeter I3I does not register or registers excessively, the operator will know that the system is defective and will proceed to make the necessary correction, until upon pressing the button I23 proper current will flow through and is registered on the instrument.

(b)' After such a preliminary test shows the protection loops are in proper condition, the spring motor is'wound by turning the key I62 with its shaft II in a clockwise direction (Figs. 3; 4'; 6', 10, 11' and '12) as shown by the arrow in Fig. 12.:

( o) Winding or the motor causes a release 75:

vented the armature I43 ture I43, lifts the detent I answer mechanically of: detent mechanism, so. that when the.- hand. is removed fronrthekey I62, themech anism. will turn the code Wheel I one revolution to give ae predetermined ignal to the central or observation station. through the lines 3, 4. Fully winding the motor causes the shaft I 5I, through connections presently described, to turn the latch plate I16 (Figs. 4 and. 6) to the left so that its bevel edge IBOengages the end of the arm. I19, by which the arm is lifted up into position in the notch I18 of the latch plate, thereby releasing the detent I44, 0n the armature I43, from the abutment member I15. To secure this result the cross pin I82, on the end of the shaft I5I, when the motor is fully wound, engages the pin I84 on the cam I03 to turn the cam until its hook surface engages the pin I84 on the latch plate I16. Thus when the motor is fully rewound it automatically and mechanically causes a release of the detent mechanism leaving the motor free to turn the code wheel I. Then as the motor turn under the influence of its spring in a counterclockwise;direction (Figs. 3, 4, 5, 10, 11 and.12)' the cross pin. I82 on the shaft I5I will back. away from the pin I84 on the cam I83 While the pin I86 on-the: shaft I5?! (Figs. 6 and will engage the lower point of the cam plate I81 attached. to the latch plate I16 to swing the latch plate OlltWZJdlYl'tOr release the arm I04, permitting the armature. I43 to fall and bringing the detent I44 into engagement with the abutment I15 on the escapement balance to stop the operation of the mechanism. Thus the motor is stopped mechanically after it has turned the code wheel one revolution to give an initial signal.

((2) A the spring motor unwinds to give'the preliminary signal, the cams 2 and I50 are turned to the position shown in Fig. 11. Thisv operation causes the high surface of the earn 2 to engage its brush, closing. the contacts I20, I2I to connect the feed line to the loop circuits and to close the contacts 98; 99 in the test cir-' cuit. During the whole of the initial movement of the shaft I5I, under the influence of I the spring, the high surface of the cam I50. has held the contacts I and I48 apart. This has prevented the setting up of a self-holding circuit, which otherwise would have occurred and prewith its detent arm I44 from droppingto stop the motor; If this circuit had not been held open by means of the cam 150, the motor would not have stopped until completely unwound.

(6) Immediately after the operator has wound the spring motor and has taken his hand from the key I62, he closes the door I51 (Figs. 1 and 2) and thedog I59 is overthrown to depress the lever I60, thereby closing the manual switch 93' (Figs. 2' and 4).

(f) In the meantime an observer at the central station has received: the signal transmitted by the. code wheel I and has impressed upon the line 4a potential of audio frequency which sounds the buzzer 95. The receipt of this signal indicates that the entire system is in proper working condition to respond for protection purposes.

'(g) The spring motor may now be released through the relay I35, which in lifting its arma the abutment member I15 on the escapement balance I13. When the brush I20 hasbeen'cl'osed on the contact I2I, as it will be after the pre-' liminary operation of the mechanism (Fig. 11)", current will flow from the batter'y through the 44 out of the path of,

aeimti lines H9 and I22, through the relay I26, the loop H8, the relay I29 and the loop II'I back to the battery to complete the circuit; the arrangement being such that the current is sufficient to lift the armature I34 of the relay I29 but insufficient to lift the armature I33 of the relay I26.-

(it) Two circumstances will cause the relay I35 to be energized. ne of these circumstances is a shunt in the protection circuit, which may occur from a tampering with the system. Such a shunt may be sufficient to cause the relay I26 to lift its armature I33 to make contact'with the point I45.

(i) Another circumstance which will cause the relay I35 to lift its armature and thereby release the spring motor is a break in the protection or loop circuits. Such a break will cause the relay I29 to drop its armature I34 on the point I36, thereby closing a circuit to the armature I35.

(7') Immediately upon action of the relay I35 in lifting its armature, a holding circuit is set up. As shown in Fig. 11, after the initial signal the brush I48 is on the edge of the high surface of the cam I55, whereby further movement causes the brush to move to the low surface of the cam I50, thereby closing contacts I46, I58. This arrangement prevents anyone from quickly breaking the circuit and then closing it again before the mechanical latch, described in the next paragraph, becomes effective.

(It) The mechanism is' arranged to latch itself open during the second operation of the motor. The latch plate H6 is released to move inwardly under the influence of its spring I89 to catch the end of the arm H9 in the notch I18. This occurs before the high surface of the cam 2 moves away to release the brush I20. Thus, the motor after it is once released by the relay I35, is kept released, first by the holding circuit and then by the mechanical latch, until its spring spends itself. As soon as the brush I 20 is released it meets the contact I52 closing the alarm circuit and causing the bell II3 to ring until that circuit is disconnected by the switch I52a.

Of course the loop circuit will be broken normally by the authorized opening of the premises in th morning. Thus the cycle is completed, either by accident or by tampering, or by the usual opening of the premises at the usual hour, through shunting or breaking of the loop circuit.

It will be apparent that various changes may be made in the details of construction, within the scope of the appended claims, without departing from the spirit of this invention, and that parts of the invention may be used to advantage without the whole.

I claim:

1. In a burglar alarm system having a transmitting station and a transmitting circuit from said station the improvement comprising a code wheel for initiating a signal through the circuit, a spring motor for operating said wheel, a cam on said motor automatically positioned according to the condition of the motor, a motor controlling path at the transmitting station, a signal receiving test circuit path at the transmitting station, and switches in said control and signal receiving circuits respectively operable simultaneously by the cam, the cam being so constructed and arranged as to close said switches when the motor is wound and in condition for operating said wheel.

2. In a burglar alarm system, a control circuit, a settable spring operated code transmitter responsive to said control circuit, a power supply for said circuit, an automatic switch in said circuit connected and arranged to close the control circult and connect it with said power supply upon the setting of the transmitter, a manually operable test switch in parallel with said automatic switch arranged and adapted to connect said circuit with its power supply while said automatic switch is open, and an ammeter in said circuit.

. 3. In a burglar alarm system, a control circuit, a code wheel, a spring motor for operating said wheel and adapted when wound to initially operate said wheel and remain in condition for subsequent operation responsive to the control circuit, an alarm circuit, a switch in the alarm circuit, and a cam associated with the motor and adapted to maintain the switch open during a period commencing during the initial operation and ending after the start of said subsequent operation and to close the switch during the remaining portion of a cycle of the motor.

4. In a burglar alarm system, a control circuit, a code wheel, a settable spring motor responsive to the control circuit for operating said code wheel, an alarm circuit, an automatic switch in the control circuit, an automatic switch. in the alarm circuit, and a cam associated with said motor and adapted to open one automatic switch and close the other simultaneously and vice versa.

5. In a burglar alarm system, a control circuit, a code wheel, a settable spring motor responsive to the control circuit for operating the code wheel, an alarm circuit, an automatic switch in the control circuit, an automatic switch in the alarm circuit, and a cam associated with said mechanism and adapted to open one automatic switch and close the other simultaneously and vice versa, the switch in the control circuit being closed and the switch in the alarm circuit being opened after the commencement of an initial operation of the code wheel and reversed after the commencement of a subsequent operation of the code wheel.

6. In a burglar alarm system, signalling mechanism comprising a spring operated code transmitter, a relay having an armature arranged and adapted as a detent for the mechanism releasing the mechanism when the relay is energized, an energizing circuit for the relay, a holding circuit for the relay, an automatic switch in the holding circuit, and a cam associated with the mechanism for operating the switch.

7. In a burglar alarm system, signalling mechanism comprising a spring operated code transmitter, a relay having an armature arranged and adapted as a detent for the mechanism, to release the mechanism when in up position and to be drawn up when the relay is energized, an energizing circuit for the relay, a holding circuit for the relay, an automatic switch in the holding circuit, a cam associated with the mechanism and operating the switch, a feed line for the energizing circuit and the holding circuit, an automatic switch in the feed line, and a cam associated with the mechanism and operating the last mentioned switch, the cams being constructed and arranged to first close the holding circuit after an operation of the mechanism following a release thereof by the armature and then to open the feed line during said operation.

8. In a burglar alarm system, a code wheel, a settable spring motor for operating said wheel, adapted upon being wound to initially operate the wheel and remain in condition for subsequent operation, a relay arranged and adapted to trip the motor, a feed circuit, a control circuit supplied by the feed circuit, a relay in the control circuit, an energizing circuit for the first mentioned relay eontrolled by the second mentioned relay and fsnpplied by the feed circuit, an automatic switch in the ifeed circuit, and a cam associated with the motor and adapted to close said switchafter the commencement of an initial operation of the code wheel and to maintain the switch closed until the beginning of a subsequent operation of the wheel.

' 9. In a burglar alarm system, a code wheel, a spring motor'for operating the wheel, a detent for the motor, a latch for securing the detent in non-holding position, means to move the latch to operative position upon winding the motor, means to move the latch to inoperative position after a predetermined operation of the motor and to release the latch after the commencement of a subsequent operation, and a relay having an armature connected with the detent for movement thereof, whereby the detent will release the motor for operation responsive to the relay and the detent will then be latched in released position.

l,0. In a burglar alarm system, a code wheel,

'a spring motor for operating the wheel, a detent for the motor, a latch for securing the ,detent in non-holdin position, a relay to move the detent, means responsive to the operation of the motor "to release the latch to holding condition, a feed circuit for the relay, a switch in the circuit, and

a cam associated with the motor for operating the switch, whereby upon operation of the relay, the motor is released by thedetent responsive to the relay and the detent is latched in non-holding position prior to Operation of the cam switch to-open the relay feed circuit.

11. In a burglar alarm system having a transmitting station and a transmitting circuit from said station, the improvement comprising a code wheel for initiating a signal through the circuit, a spring motor for operating said wheel, a path for a circuit controlling the motor, a signal receiving test circuit path at the transmitting station, switches in said control and signal receiving circuit paths respectively. and means connected to and operated by the motor for closing said switches simultaneously when the motor is wound and in condition to operate the code Wheel.

12. Ina burglar alarm, a code wheel, a spring motor adapted when wound to initially operate the wheel and remain in condition for subsequent operation, a transmitting circuit interrupted by said code wheel, a circuit controlling the motor, a signal receiving test circuit, switches in said circuits respectivelyjand means connected to and operated by the motor for closing said switches simultaneously when the motor has initially operated the wheel and is in condition for subsequent operation as aforesaid.

CHARLES E. POTTER.

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