US1918240A - Police signal system - Google Patents

Description

ly 1933- G. F. c. BAUER POLICE SIGNAL SYSTEM Filed March 26, 1931 2 Sheets-Sheet l w m 3 W. W .w 3 W J a 0 C M J w 1 m M 3 W A. ,2 i1 ww 1- EEIEE -4 F Z a y w 4 3a, m dm w m T w 61cm wags July 18, 1933.

G. F. c. BAUER 1,9182% POLICE SIGNAL SYSTEM Filed March 26, 1931 2 Sheets-Sheet 2 Patented July 18, 1933 UNITED STATES PATENT FFICE GUSTAV F. C. BAUER, OF TONI-RWANDA, NEW YORK, ASSIGNOR TO NATIONAL POLICE SIGNAL COMPANY, OF BUFFALO, NEW YORK, A UORPORATION OF NEW YORK PSLICE SEGNAL SYSTEM:

Application filed March 26, 1931.

This invention relates to an electrical signaling system and more particularly to a system of this character for use between a central station and a plurality of substations for police purposes.

The system is a simplification and improvement of the systems described in Patents No. 1,080,018, Louis 1V. Miller, December 2, 1913; 1,218,682, Louis Miller, March 10 13, 1917 1,552,843, lVilliam W. Kideney and Gustav F. C. Bauer, September 8, 1925; 1,793,042, Gustav F. C. Bauer, February 17, 1931, and 1,797,281, Gustav F. C. Bauer, March 24:, 1931.

Such police signal systems include a plurality of telephone circuits between a central station switchboard and a plurality of police boxes or substations so that a telephone conversation can be carried on between the central station and any of the substations and means for giving either a periodic audible or a periodic visual signal from the central station at any of the substations so as to call the nearby ofiicer to the substation or police box for the purpose of giving him instructions. Provision can also be made for enabling wagon calls to be made at each police box and to permit of periodical reports to be made at each box and automatically recorded at the central station but as these latter form no part of the present invention they are not shown nor described.

For reasons which will presently appear, a in such systems as heretofore constructed,

such police signal systems required heavy cables as compared with commercial telephone cables and also could not be used in association with regular telephone circuits 40 because of the inductive eiiect on adjacent pairs of wires in the cable. This required the installation of special equipment throughout and made such systems too costly for smaller cities.

The principal object of the present invention, therefore, is to provide such a police signal system which can be used in connection with ordinary commercial telephone cables thereby permitting smaller communities to avoid the heavy cost of laying spe- Serial No. 525,471.

cial cables and permitting them to' rent commercial telephone circuits for this purpose.

Another object is to simplify the equipment as much as possible by eliminating the usual line jacks and interconnecting cords and plugs in installations for smaller communities. In police signal work, as distinguished from standard telephone practice, the telephone calls originate either at the switchboard or at one of the police boxes and the switchboard is merely a terminalpoint and not a switching point. This is particularly true in police signal installations where only one switchboard is used to cover an entire community. Hence by eliminating the necessary jacks, cords and plugs in smaller community installations, the equipment provides full police signal service without the extra cost and upkeep which this extra equipment entails. Vhere, however,- more than one switchboard installation is essential, as where the community has several police stations, then line jacks and interconnecting cords and plugs are required for intercomnecting the various departments and for direct service between the switchboards and all boxes and lines. The fundamental features of this invention which permit the use of commercial telephone cables can also be embodied in such systems for large communities as re quire the necessary jacks, cords and plugs for full interconnecting telephone service throughout.

Another purpose is to provide a system in which by the use of small signal energy, there are no disturbing inductive effects set up in adjacent circuits in a common cable nor are high voltage surges created as might injure the line conductor insulation.

Another purpose is to employ an ionized gas lamp as a visual signal or target at the box, the use of which results in a number of important advantages, the most important of these being that such a lamp has a definite starting voltage below which it will not function. Inasmuch as this starting voltage of the lamp can be made considerably higher than the voltages of the common. battery or telephone currents, such a lamp can be connected directly across the telephone line-circuit without reducing, in any way, the efiiciency of speech transmission over the circuit.

Another purpose is to provide enclosed mercury tube switches for the telephones at the boxes, such switches not being affected by climatic conditions to the same degree that mechanical switches are. 7

Still further objects are to provide switchboard equipment which can be made extremely compact, which is reliable and efficient in its operation and will not readily get out of order and in which there is the minimum chance of confusion in the operation of the central station switchboard.

In the accompanying drawings:

Figure 1 is a diagrammatic representation of that portion of the police signal circuit Which is arranged at the central station.

Figure 2 is a diagrammatic representation of that portion of the police signal system which is arranged at the substation or box.

Figure 3 is a simplified diagrammatic representation of the talking circuit alone.

Figure 4 is a side elevation of an ionized gas lamp suitable for use as a visual signal at each police box.

Figure 5 is a top plan view thereof.

Figure 6 is a side view of one of the elec-. trodes before being shaped.

Police signal systems, as heretofore constructed, had numerous difficulties and defects.

In such systems, the standard practice has been to employ a combination of a grounded lamp as a visual and a horn or howler across the telephone circuit as an audible signal. It has heretofore also been standard practice to employ a tungsten filament lamp. Such a lamp has several peculiar characteristics. Its cold resistance is aproximately one-seventh its hot resistance, it also gives a white light, a red light being necessary for police signal work for distinctive visibility. If such a tungsten filament lamp were used across the telephone circuit, it was essential to block the telephone current from this part of the circuit. Such an organization required a relatively large condenser making an electrical combination, particularly in view of the cold resistance of the lamp, too low for efficient telephone service inasmuch as this path was a drain on the talking currents across this part of the line. Therefore, it has been heretofore necessary to use the horn-and its condenser across the line, taking advantage of the high impedance of the horn to prevent a hy-pass of the talking currents.

However, the horn across the circuit gave a disagreeable effect which required additional apparatus at the central station to eliminate. Inasmuch as the horn was flashed on and oil there developed at the cutting of? point a high inductive surge and this surge had to be drained off of the line before the circuit was reestablished to its normal condition. If these high inductive surges were not drained off, they created acontinual slap of the line relays, affecting their permanent adjustment and they also accidentally operated accessory equipment.

The desirable method of operation would be the lamp and condenser across the line but the results were unsatisfactory because of the low voltage by-pass which this cross circuit offered and also since the'condenser was necessarily more or less abnormally large, it reduced the lamp voltage to a large extent.

Another defect resulting from the use of a tungsten filament lamp was that the lamp generally employed used 15 Watts of energy but when enclosed in a red globe to give a distinctive signal visible both at day and at night, the red globe filtered. out 80% of the light energy ofthe lamp leaving only about 3 watts of light energy available for signaling purposes. Moreover, the blocking of the light through the accumulation of dirt under these circumstances was intensified. considerably because there were three surfaces on which dirt could collect: the in and outside of the red globe and the outside of the'lamp.

The important defect for smaller community equipment, however, was that as a 15 watt lamp was the smallest practical size to use, the horn used as an audible signal was also developed to operate on the same wattage. From an operating standpoint, the energy consumption of both the lamp and the horn made it necessary to use a relatively large size conductor so that reasonably long distances could be efficiently covered. As these distances increased, the inductive surge in cutting the horn off also increased and there fore the cable insulation had to be relatively heavy to prevent puncturing of the insulation. This made it essential for good operation to construct, lay and install special wire and cable equipment and unfortunately existing wires, such as those used by telephone companies, could not be used, first, because the conductor size was too small, secondly, because the conductor insulation was in most cases of such a character that it would be doubtful whether it would stand up under the inductive surges referred to and, thirdly, because mixing of the two classes of service (commercial telephone and police signal) was undesirable because these inductive surges would react on the other pairs of commercial telephone conductors in the same cable.

The present invention proposes to elimi natc these defects by employing an ionized gas lamp across the line as a target or visual signal and by employing a grounded electromagnetic horn connected to one side of the line, this horn being operated in response to one side of the frequency of the alternating current employed. The use of an ionized gas lamp, eliminates all of the above defects, the

more particularly in that such a lamp has a definite starting voltage below which it will not function, and since this can be made to be more than the voltages of the telephone currents, such a lamp can be connected directly across the telephone line circuit without reducing, in any way, the efliciency of speech transmission over the circuit. By the selection of a suitable gas, such as neon, for the lamp it can also be made to give a distinctive signal which is clearly visible both by day and atnight.

The telephone circuit The central station circuit shown in Fig. 1 and the police box or substation circuits shown in Fig. 2 are connected by the usual telephone lines each comprising a tip site and a ring side 11. At the police box, a telephone receiver 12, hook switch 13 and transmitter 14 are in circuit with the ring and tip sides of the line circuit, these elements being arranged in the usual manner so that when the receiver 12 is removed from the hook, the hook switch 13 closes and an electrical circuit is established between the ring side of the line circuit, transmitter 14, receiver 12 and tip side of the line circuit. Instead, however, of employing the usual mechanical hook switch, the hook switch 13 is preferably of the enclosed mercury contact type in which the contacts of the circuit are passed through the sides of a sealed glass tube containing a globule of mercury which rolls to connect the two contacts when the receiver is taken oil the hook. Such a switch is less susceptible of getting out of order and has been found entirely satisfactory in installations made according to the invention. At the central station 1) the ring side 11 of the line circuit is connected with one armature 15 of a line relay 16, this armature 15. normally or in the deenergized condition of the line relay 16 being held in contact with a wire 17 which connects with the ring spring contact 18 of the line key 20. This line key 20 is designed so that when the key is thrown up. the group of spring contacts 18, and 51 are moved downward and when the key is thrown down the spring contact is moved upward. The key 20 as shown is in its normal inoperative position. The wire 17 is also connected through the windings 21 of a relay 22 with a grounded battery B.

The tip side 10 of the line is connected with the other armature 23 of the line relay 16, this armature normally or in the deenergized condition of the relay 16 being held in contact with a wire 24 which connects with the tip spring contact 25 of the line key 20. This line key wire 24 is connected through the windings 26 and wire 27 with ground.

Vhen the line switch key 20 is thrown up, the spring ring contact 18 is moved into engagement with a spring contact 28. This spring contact 28 is connected by a line 29 with the transmitter 30 and receiver 31 of a switchboardtelephone set 32. This telephone set is shown as being ofthe continental type and the other terminal of the receiver 31 is connected by a line 132 with a spring contact 33 of the line key 20. The spring contacts 18 and 25 of the line key 20 are connected by an insulated block 34 so that when the key 20 is thrown up and the contacts 18 and 28 engaged, the contact 25 is also moved into engagement with the contact 33, whereby the receiver and transmitter of the switchboard set are placed in circuit across the line.

The wire 29 is also connected by a wire 35 with the hook switch 36 of the switchboard telephone set 32, this hook switch 36 being closed when the receiver 31 and transmitter 30 are hung up and open when the transmitter and receiver are in use. This hook switch 36 also connects with a grounded buzzer 38. A white lamp 40 is associated with each line circuit and corresponding key 2O on the switchboard to indicate the particular boX calling. This white lamp 40 is lighted through the action of an armature of relay 22, this armature being continually connected by a wire 46 with the grounded wire 27 When the relay 22 is energized, the armature 45 is drawn up and is connected with a contact 47. The contact 47 is connected with one side of the white lamp 40 by a line 48 and the other side of this lamp is connected by a line 49 with the spring contact 50 of the line key 20. This spring con- 100 tact 50 is normally in engagement with a spring contact 51 which spring contact 51 is connected by a wire 52 with the windings 53 of a relay 54. These windings 53 also con nect by a'wire with a battery B the op- 105 posite side of which is grounded. Vi ire 52 and relay 54 are common to all lines. This relay 54. when energized, draws up an armature 56. this armature being connected to the wire 55 and moving into'eng'agement with a no contact 57. This contact 57 is connected by a wire 58 with the wire 37 and buzzer 38. The spring contact 51 of the line key 20 is connected to the contact 25 by an insulating block 59 so that when the line key 20 is thrown 115 up the spring contact 51 is thrown out of engagement with the spring contact 50.

Operation of 25. w telephone circuit hen the policeman at the police box wishes to talk with the switchboard operator, he lifts the receiver 12 at the box. This establishes a circuit through the battery B windings 21 of relay 22, wire 17, armature 15, ring side 11 of line, transmitter 14, receiver 12, mercury switch 13, tip side 10 of line, armature 23. wire 24, windings 26 of relay 22 and wire 27 to ground. The energization' of the relay 22 pulls up the armature 45 into contact with the contact 47 and a circuit is 139 -established through battery B windings 53 of relay 54, wire 52, spring contacts 51 and 50 of the line key 20, wire 49, white lamp 40, wire 48, contact 47, armature 415 and wires 46 and 27 to ground. At the same time the white light 40 is energized, the energization of the relay 5a pulls up the armature 56 and establishes a circuit from battery B wire 55, armature v56, contact 57, wire 58 and buzzer 38 to ground.

The buzzer 38 calls the switchboard operators attention to a call coming in and the white light 40 identifies the boX calling and its associated key 20. The operator thereupon throws the corresponding line key 20 up and lifts the receiver and transmitter of his telephone set 32 to answer the call.

Throwing the line key 20 up, through the insulating blocks 3 1 and 59 breaks the connection between the spring contacts 50 and 51 and thereby breaks the current supply from battery B" to the white lamp 10. At the same time this breaks the current supply from the battery B through the windings 53 of the relay 54: so that the armature 56 re turns to normal and breaks the current supply from battery B to the buzzer 38.

The switchboard operator then receives the message, the talking circuit comprising (as best shown in Fig. 3) ring side 11 of the line circuit, wire 17, closed spring contacts 18 and 28 of the switchboard key 20, wire 29, switchboard transmitter and receiver 30 and 31, wire 132, closed spring contacts 33 and 25 of the switchboard key 20, wire 24, tip side 10 of line, hook switch 13 at the box, box receiver 12 and transmitter 14 to ring side 10 of line. This circuit is fed by battery across the line. It will be noted that the supply of battery current from the battery B differs from standard telephone practice. Upon reference to Fig. 3, it will be noted that the battery B is connected across the ring and tip sides of the line circuit so that the talking circuit is normally, or in its inoperative condition, impressed with battery current and the battery current for the operators set is derived from the cord circuits. Vith the present system also, a single key 20 is employed to send both signalling energy over the corresponding line and also to set up the line for talking. When the conversation is finished, both parties hang up, the apparatus thereby being restored to the normal inoperative condition which it had before the patrolman put in his call.

When the patrolman hangs up if the switch, board operator fails to throw the key :20 back up to normal, the buzzer 38 will continue to buzz, it being then supplied with energy from battery B, windings 21 of relay 22. wire 17, closed spring contacts 18. and 28 of the line key 20, wire 29 and 35, closed hook switch 36 and wire 3'? to buzzer 38. The buzzer 38 thereby serves as a signal to insure that the line keys 20 are returned to normal after a conversation 1S finished.

The signaling circuit Adjacent each box an audible signal comprising an electric horn 60 and a visual signal 61 are mounted, these two signals being so arranged as to be visible and audible at a distance from the box, their purpose being to call the patrolman to the box in order to give him instructions.

The horn or howler 60 is of the electromagnetic alternating current type and consequently its pitch is determined by the frequency of the alternating current operating it. To secure the desired frequency, the current is supplied, as hereinafter described, from a motor-generator unit which supplies the current at 150 cycles, thereby providing a frequency of 300 sound vibrations per second. Electrical frequency when directly converted into sound energy has the etfectof creating a sound pitch of double the frequency of the electrical energy due to the fact that the negative electrical impulse creates one sound impulse and the positive electrical impulse creates another sound impulse and since one cycle consists in one negative and one positive impulse, one cycle in the frequency of he electrical energy creates two sound impulses cf the same character. The horn 60 is connected by a wire62 to the tip side 10 of the line and its other terminal is grounded.

The visual signal 61 is connected across the line by wires 63 and (Set. This is possible in the present system since the signal 61 is not a filament lamp but is an ionized gas type lamp.

In Figs. 46 a form of lamp particularly suitable for use as a target is shown. This lamp has the conventional Edison base. The base carries a clear glass globe 68 which is hermetically sealed to the base and is filled with a gas to obtain the desired color. Neon gas is the best suited for the present use since it gives a color approaching the red heretofore used as visual signals in systems of this character and forms a distinctive target. Rising from the base within the globe is a glass pillar or column 69 on which the two electrodes 70 are supported. These electrodes are semicylindrical in shape and are supported at their opposite ends by wire supports 71 set into the glass column 69. Two

of these supports form the leads 72 and 73.

each lead being connected with a corresponding electrode and one of the leads connecting with the screw sheath 66 while the other connects with the central contact 67 of the bulb.

The two electrodes are spaced apart andeach is provided with a number of relatively large sized perforations 74 over its entire surface. These perforations can be stamped, as indicated, or the electrodes can be made of large mesh screen. The purpose of these perforations is to provide a larger area for the same size of electrode, thereby obtaining a larger target and a target-more visible at distance than a smaller imperforate electrode of the same area. Monochromatic light has a tendency to appear to blend when viewed at a distance. Thus two sources of monochromatic light at a distance appear as a single enlarged source of light whereas light of two colors at a distance tends to separate. Therefore the present perforated electrodes, at the distance from which they are usually viewed, will appear as a single large electrode or target of light which is easily discernible in the daytime and of a distinctive color and quality.

The source of alternating current for the operation of the visual and audible signal comprises a motor 75 directly connected with a generator 76 and the generator shaft 77 through a train of gears (not shown) drives a flasher contact shaft 7 8 which carries the contacts of a flasher. One terminal of the motor '75 is connected to one commercial power line 79 usually supplying cycle current at 110 volts and the other motor terminal is connected to the other commercial power line 80 through a wire 81, spring contact 82 of a power key 83, and a second spring contact 8 1 of this same key 83. The key 83 carries a second set of spring contacts 85 and 86 and the spring contacts 8 1 and 86 are arranged to work in unison and both close with their corresponding contacts 82 and 85 upon throwing the key 83 down.

The spring contact 86 is connected with a battery B and its corresponding spring contact 85 is connected by a line 87 with a primary flasher contact 88 mounted on the flasher contact shaft 78. This primary flasher contact 88 is metallic and is in the form of an ext-ended cam which on each revolution of the shaft '78 engages a contact finger 89. This contact finger 89 is connected by a wire 90 with the upper contact 91 of the line key 20 and when this line key is thrown up this spring contact is engaged by a second spring contact 92. This spring contact 92 is con nected by a wire 93 with the wire 94 one end I of which wire 9-1 is connected with the red switchboard lamp 95, the other terminal of this red lamp being grounded. The wire 94 also connects with the windings 96 of the line relay 16 and these windings connect with a wire 97' which terminates in a contact 98 normally engaged by the armature 4-5 of the relay 22.,

another lamp 99 is employed at the switchboard in the signal system, this lamp 99 having one of its terminals grounded and the other being connected by a wire 100 with the wire 87.

The flasher includes a secondary flasher contact 101 which is also mounted on the flasher-contact shaft 78 adjacent the primary rotary flasher contact 88. This secondary contact is also in the form of a metal cam but is shorter in its effective length than the primary flasher contact 88, the primary flasher contact 88 acting, through battery current, to set the circuit up for signaling and the secondary flasher contact 101 sending generator current over the set up circuit. By setting up and breaking the signaling circuit in advance of sending generator current over it or cutting off the generator current (by the larger size of the primary flasher con tact 8S) arcing of the contacts on relay 16 is avoided.

The secondary flasher contact 101 is continually connected by a wire 102 with the central spring contact 103 of a key 104. This key 1 is a non-holding key and upon being released immediately assumes its normal position shown in which the central spring contact engages a spring contact 105 and is out of engagement with a. spring contact 106. The spring contact 106 is grounded and the spring contact 105 is connected by a wire 107 with a contact 108, this contact 108 being engaged by the armature of the line relay 16 when this line relay 16 is energized and the armature 15 drawn up.

The secondary flasher contact 101 on the flasher cont-act shaft 78 contacts with a contact finger 109 which is connected by a wire 110 with one terminal of the 110 volt 150 cycle generator 76. The other terminal of this generator is connected by a wire 111 with a contact 112, this contact 112 being engaged by the armature 23 of the line relay 16 when this relay 16 is energized and the armature 23 is drawn up.

Operation of the signaling circuit call a patrolman to his box to give him instructions, the operator throws the master key 83 down and also throws downthe keys on such lines as he desires to'use. this combination, the circuit arrangement is such that the visual signals of these lines will function in synchronism with the flasher operation. This establishes contact between the corresponding spring contacts 91 and 92; 82 and S4; and 85 and 86. The motor 75 is thereby energized from the commercial power lines 79 and 80, through a circuit comprising a commercial power line 79, motor 75, wire 81, springcontacts 82, 84 of key 8 3 and commercial power line 80.

The energizationof the motor 75 starts the rotation of the generator shaft 7 7 which drives the primary rotary'flasher contact 88 and the rotation of this primary flasher contact 88 operates to set up periodically the signaling circuit for sending signaling impulses over the particular line circuits selected. In

so setting up the line circuts over which the signaling impulses are to be sent, thecurrent With When the switchboard operator wishes to from battery B passes through the closed spring contacts 85 and 86 of the key 83, wire 87, flasher contact 88, contact finger 89, wire 90, closed spring contact fingers 91 and 92 of the set up line keys 20, wires 93 and 94, grounded red lamps 95 and windings 96 of the line relays 16, wires 97, contacts 98, armatures 45, and wires 46 and 27 to ground. The energization of the line relays 16 draws up the armatures- 15 and 23, thereby disconnecting the entire talking circuit and setting up the signaling circuit.

The rotation of the generator shaft 77 operates the generator 76 and also rotates the secondary rotary flasher contact 101. When this occurs, generator 150 cycle current of 110 volts flows from the generator 76, wire 110, contact finger 109, secondary rotary flasher contact 101, wire 102, closed spring contact fingers 103 and 105 of key 104, wire 107, contacts 108 of the set up line circuits, armatures 15 of energized line relays 16, ring sides 11 of line, ionized gas lamps 61 (Fig. 2) tip sides 10 of line, armatures 23 of energized line relays 16, contacts 112, and wire 111 to the other terminal of the generator. Each time the flasher contact shaft 78 rotates it sets up the signaling circuit through the primary rotary flasher contact 88 and subsequently sends out a signaling impulse over the set up circuits through the visual signal light 61. The visual signal lights 61 of the set up circuits therefore flash on and oil periodically until the patrolman answers the call.

The visual signal 61 at the box is not always within view of the patrolman and it is therefore necessary to give a few blasts on the horn 60, to call his attention to the fact that he is wanted at the box. This cannot, however, be continued as the periodic blast of the horn or howler is extremely annoying to the residents near the box if its operation is continued for any substantial period of time. To give a few blasts on the horn, the operator throws up the non-holding key 104 for a short time and then releases it to its normal position'shown. So doing breaks the contact between the spring contacts 103 and 105 and establishes it between the spring contacts 103 and 106. When this is done a circuit of 150 cycle current is established through ground, spring contacts 106 and 103 of key 104, wire 102, secondary flasher contact 101, contact finger 109, wire 110, 150 cycle generator 76, wire 111, contacts 112 of relays 16 of the set up circuits, armatures 23, tip sides 10 of lines, wires 62 and through the horns 60 to ground.

WVhen the desired number of blasts have been given, the operator releases the key 104 and the periodic operation of the visual signal 61 is resumed until the patrolman answers the call.

The use of the master key 104 for changing from visual t'o audible signals over one or more line circuits is covered in the patent of Gustav F. C. Bauer, No. 1,797,281, dated March 24, 1931.

It will be noted that during the signal intervals, line relays 16 break oif the normal talking circuits and equipment at the central station. This is purposely done to prevent the high voltage current from backing up through any of this apparatus. However, during this interval, this equipment cannot function. Therefore when a patrolman answers during the signaling interval he cannot reach the central station. However, as the signaling intervals are purposely made to extend over a period of one-half second and as the silent intervals are of approximately the same length, these non-operative intervals of the talking circuit are merely momentary and have no effect on the operation of the system. Thus between each signaling period, the line relays 16 of the set up circuits are in their normal non-operative positions and as soon as the patrolman lifts his receiver, a circuit is established, at the first non-signaling interval, from battery B, winding 21 of line relay 22, wire 17, armature 15 of line relay 16, ring side 11 of answering line, transmitter 14, receiver 12, tele phone switch 13, tip side 10 of line armature contact 23 of line relay 16, wire 24, winding 26 of relay 22, wire 27 to grounded side of battery B. This energizes relay 22 and draws up its armature 45 and breaks the grounded side of the circuit of relay 16 at contact 98 thereby preventing the further operation of relay 16 to send more signaling impulses over the line and establishing the normal talking circuit as previously described.

The substitution of the ionized gas type of lamp 61 for the usual tungsten filament lamp eliminates all of the ditficulties of the older system previously referred to, and in addition some peculiar advantages are gained.

In the first place, with the ionized gas type of lamp in which two electrodes are contained within the globe, the desired color can be obtained by employing a rarified gas that will give this color. It was also discovered in experimental work that such a lamp made to operate at 110 volts has an entirely different reaction to lower voltage than a tungsten filament lamp. In the filament type of lamp, the lamp has a definite resistance which varies according to temperature but a current of any voltage wil flow through the filament. With the ionized gas lamp the gas does not become a conductor until a voltage has been reached which will ionize the gas between the two electrodes and from then on any voltage upward will operate. In the lamp used in the present case, this cutting ofl point should be around 40 volts or higher because the direct current voltages used do not exceed 24 Volts. This results in such a lamp being a completely open circuit for any current whose voltage does not exceed the initial starting voltage required by the lamp. Therefore with a lamp of this type it is possible, as shown to connect it directly across the talking circuit and the only loss of talking energy is the efiect within the lamp of the two electrodes acting as a condenser. The capacity of the lamp as a condenser when not in operation is so low as to have no measurable effect in absorption of the talking energy. lVith the present system, therefore, we are enabled to place the lamp directly across the talking circuit without any effect on the talking currents and at the same time completely blocking off the flow of the relatively low voltage battery current through the lamp. I/Vith the filament type of lamp it would be necessary to include a condenser in the lamp circuit to obtain the same result. Inasmuch as the capacity reaction ofthe lamp is exceedingly small there are no surge effects upon the line.

Inasmuch as a fairly goon red can be obtained by the use of neon gas in the lamp 61, the use of a red globe, which was required with a tungsten filament lamp is eliminated. This eliminates the red globe necessary with a white light and its loss through absorption which amount to of the total energy. Therefore where a tungsten filament lamp of 15 watts was required to providelight equivalent to a 3 watt lamp, with the ionized gas type of lamp, the energy consumption can be cut down to 5 watts. This permits of using such a combination over the smaller standard sizes of conductors used in commercial telephone practice and with the voltages used in the other equipment, the systenrcomes well within the limiting requirements of telephone practice.

The amount of energy determined upon for best results is about 5 watts with an originating voltage of 110. In the lamp it is desirable to get as much lightas possible for the iamount of electrical energy consumed and since the lamp is not for the purpose of illumination but merely as a visible target, advantage has been taken of the peculiar irradiation effect of monochromatic light which at a distance causes several. sources of light to appear to merge, By perforating the electrodes in the manner described a large elect-rode area can be obtained without loss in light and thereby provide a large and more distinctive target without increasing the energy required.

lVith the drop of from 1 watts of energy to 5 watts, a gain is made in the lamp by the use of gas in place of a filament and the elimination of the red filter. However, with the horn, the area over which it will be heard is restricted and as it is desirable to use the same energy consumption in the horn as in the lamp, in the present installation, advantage is taken of the fact that as the pitch of the sound is increased the amount of energy necessary to cause it to cover the same area can be decreased. Therefore it is desirable to use a current source having a frequency of approximately 150 cycles or higher which frequency will operate to advantage both with the lamp and the horn. With the lamp only one electrode is illuminated at a time and only during that part of the voltage wave or curve above the initial ionization point so that the lamp is fully illuminated only one-quarter of the time so that with 150 cycle current these impulses come muchcloser together and the overall illuminated effect is much better than at lower frequencies. lVith the electromagnetic type of horn, the sound frequency is double the electrical frequency, as previously pointed out, so that with 150 cycle current, 300 sound impulses per second are produced which is sufliciently high pitched to cover the desired area even though the horn operates with less electrical energy.

The .ack of heat inertia in an ionized gas type of lamp is also taken advantage of in the present system. hen the horn is being used it is connected from one side of the line to ground and this particular part of the circuit then acts as one side of acondenser, the size of the condenser varying .as the length of the circuit. There would normally occur, therefore, at each cutting off point of the horn an inductive reaction back over the circuit which is not desirable. However, the lamp 61 across the line acts as an automatic drain for these surges and comes into action instantaneouslyfor any voltages above the ionizing voltages required to start the lamp. Inasmuch as this voltage lies, say, between 40 and 50 volts and the horn operating voltage is volts there can be no destructive surges occurring within the circuit since the instantaneous reaction of the lamp to high voltages suppresses such voltages so that they have no harmful eflects on any parts of the circuit.

7 From the foregoing it is apparent that the present invention provides a police signal system which can be operated over rented commercial telephone lines; it is extremely simple and eflicient in operation; provision is made throughout to prevent destructive surges, arcing or other reactions which would tend to reduce the efficiency of the system or put it out of order; adequate provision is made for giving a distinctive audible and visual signal at each box which can be readilydiscerned both during the day and at night and to simplify and insure the reliabi lity of the system, the switchboard has been stripped of all functions not absolutely essential to police work of this character. If desired, however, accessory equipment may be added, such as lines and jacks to permit of connecting difiierent stations with the different boxes, wagon call switches at: the

boxes, report switches at the boxes to render recorded reports at the station or other features of this character.

lVhile I have shown one embodiment of the invention it is apparent that the essential features of the invention can be embodied in systems of widely different character and the invention is therefore not to be considered as limited to any particular form but the invention is to be accorded the full scope comprehended by the accompanying claims.

I claim as my invention:

1. In combination with a common battery telephone system comprising a central station, at least one substation and a line circuit connecting said central station with said substation and said line circuit being normal ly impressed with said battery current, a signal device which within itself is a non-conductor at voltages below a predetermined value and becomes a conductor at voltages above said predetermined value and having a normal operating voltage above that of said battery, said signal device being arranged at said substation and connected directly across said line circuit, said signal device forming a completely open circuit across said line circuit at the voltages of said common battery and means at said central station for intentionally passing electrical current having a voltage in excess of that of said common battery through said line circuit to operate said signal device.

2. In combination with a common battery telephone system comprising a central station, at least one substation and a line circuit connecting said central station with said substation, and said line circuit being normally impressed with said battery current, a signal device which within itself is a non-conductor at voltages below a predetermined value and becomes a conductor at voltages above said predetermined value and having a normal operating voltage above that of said battery, said signal device being arranged at said substation and connected directly across the line circuit, said signal device forming a substantially completely open circuit across said line circuit at the frequencies of the talking currents and means at said central station for intentionally passing electrical current having a voltage in excess of that of said common battery through said line circuit to operate said signal device.

3. In combination with a common battery telephone system comprising a central station, at least one substation and a line circuit connecting said central station with said substation and said line circuit being normally impressed with said battery current, a signal device which within itself is a nonconductor at voltages below a predetermined value and becomes a conductor at voltages above said predetermined value and having a normal operating voltage above that of said battery, said signal device being arranged at said substation and connected across the line circuit, said signal device forming a completely open circuit across said line circuit at the voltages of said common battery and the speech frequencies of said talking circuit, and means at said central station for intentionally passing electrical current having a voltage in excess of that of said common battery through said line circuit to operate said signal device.

4. In combination with a common battery telephone system comprising a central station, at least one substation and a line circuit connecting said central station With said substation and said line circuit being normally impressed with said battery current, a signal lamp which within itself is a non-conductor at voltages below a predetermined value and becomes a conductor at voltages above said predetermined value and having a normal operating voltage above that of said battery, said. signal device being arranged at said substation and connected directly across said line circuit, said signal lamp forming a a completely open circuit across said line circuit at the voltages of said common battery and means at said central station for intentionally passing electrical current having a voltage in excess of that of said common battery through said line circuit to operate the signal lamp.

5. In combination with a common battery telephone system comprising a central station, at least one substation and a line cir cuit connecting said central station with said substation and said line circuit being normally impressed with said battery current, an ionized gas signal lamp which within itself 1s a. non-conductor at voltages below a predetermined value and becomes a conductor at voltages above said predetermined value and having a normal operating voltage above that of said battery, said signal device being arranged at said substation and connected directly across said line circuit and means at said central station for intentionally passing electrical energy through said line circuit havlng a su'lliciently high voltage to illuminate said signal lamp.

6. In combination with a common battery telephone system comprising a central station, at least one substation and a line circuit connecting said central station with said substation and said line circuit being normally impressed with said battery current, an ionized gas signal lamp which within itself is a non-conductor at voltages below a predetermined value and becomes a conductor at voltages above said predetermined value and having a normal operating voltage above that of said battery, said signal device being arranged at each substation and connected across said line circuit, said ionized gas lamp comprising a sealed bulb containing an electroluminescent gas and having spaced foraminous electrodes and leads connecting the electrodes with the opposite sides of said line circuit and said ionized gas lamp having a starting voltage greater than the voltage of said common battery and means at said central station for intentionally passing electrical energy through said line circuit having a sufficiently high voltage to illuminate the signal lamp.

7. In combination with a common battery telephone system comprising a central station, at least one substation and a line circuit connecting said central station with said substation and said line circuit being normally impressed with said battery current, a signal lamp which within itself is a non-conductor at voltages below a predetermined value and becomes a conductor at voltages above said predetermined value and having a normal operating voltage above that of said battery, said signal device being arranged at said substation and connected directly across said line circuit, said signal lamp forming a completely open clrcuit across the line circuit at the voltages of said common battery, a signal horn at said substation and having a vibratory sound producing member responsive to electrical frequencies and having one terminal connected to one side of said line circuit and its other terminal grounded, a source of alternating current having a voltage suiticiently high to illuminate said lamp and means at said central station for selectively passing said current through the opposite sides of said line circuit to illuminate said signal lamp or through one side of said line circuit and through said horn to ground thereby to operate said horn.

8. In combination with a common battery telephone system comprising a central station, at least one substation and a line circuit connecting said central station with said substat on and said line circuit being normally mpressed with said battery current, an ionized gas signal lamp which within itself is a non-conductor at voltages below a predetermined value and becomes a conductor at voltages above said predetermined value and having a normal operating voltage above that of said battery, said signal device being arranged at each substation and connected directly across said line circuit, said lamp having a starting voltage substantially higher than that of said common battery, a signal horn at said substation and having a vibratory sound producing member responsive to electrical frequencies and having one terminal connected to one side of said line circuit and its other terminal grounded, a source of alternating current having a voltage sufliciently high to illuminate said lamp and means at said central station for selectively passing said alternating current through the opposite sides of said line circuit to illuminate said signal lamp or through one side of said line circuit and through said horn to ground thereby to operate said horn.

9. A common battery telephone system comprising a central station, having an op era-tors set, at least one substation having a substation set, a line circuit connecting said central station with said substation, said line circuit being normally impressed with battery current, signal means connected to said line circuit at said substation, a switch key at said central station, means associated with said switch key when thrown in one direction to send signal energy over said line circuit, means associated with said key when thrown in the opposite direction to establish a talking circuit between said central station and said substation, said last named means including means supplying talking battery current to said operators set through said substation battery circuit, and means for establishing a tell-tale circuit over part of said substation battery circuit and through a part of said operators talking circuit and including a buzzer whereby when the operator replaces the receiver on its hook switch the buzzer will operate until said switch key is restored to normal.

10. A common battery telephone system comprising a central station having an operators set, at least one substation having a substation set and a line circuit connecting said central station with said substation, and said line circuit being normally impressed with battery current, signal means connected to said line circuit at said substation, a switch key at said central station, a line call signal at said central station, means associated with said switch key when thrown in one direction to send signal energy over said line circuit, means associated with said switch key when thrown in the opposite direction to establish a talking circuit between said central station and said substation and to disconnect said line call signal, and means for establishing a tell-tale circuit over part of said substation battery circuit and through a part of said operators talking circuit and including a buzzer, whereby when the operator replaces the receiver on its hook switch the buzzer will operate until said switch key is restored to normal, said switch key upon being restored to normal disconnecting said operators set and reestab-lishing said line call circuit.

11. In combination with a common battery telephone system comprising a central station, at least one substation, and a line circuit connecting said central station with said substation, said line circuit being normally impressed with battery current, and ionized gas signal lamp which within itself is a nonconductor at voltages below a predetermined value and becomes a conductor at voltages above said predetermined value and having a normal operating voltage above that of said battery, said signal device being arranged at said substation and connected directly across said line circuit, said ionized gas lamp having a starting voltage greater than that of said common battery, a switch key at said central station, means associated with said switch key when thrown in one direction to send signal energy over said line circuit, said signal energy having a voltage in excess of that of said common battery to operate said lamp and means associated with said key when thrown in the opposite direction to establish a talking circuit between said central station and said substation, said last named means including means supplying talking battery to the operators set through said substation battery circuit.

12. In combination with a common battery telephone system comprising a central station, at least one substation and a line circuit connecting said central station with said substation, said line circuit being normally impressed with battery current, an ionized gas signal lamp which within itself is a nonconductor at voltages below a predetermined value and becomes a conductor at voltages above said predetermined Value and having a normal operating voltage above that of said battery, said signal device being arranged at said substation and connected directly across said line circuit, said ionized gas lamp having a starting voltage greater than that of said common battery, a switch key at said central station, means associated with said switch key when thrown in one direction to send signal energy over said line circuit,

said signal energy having a voltage in excess of that of said common battery to operate said lamp, means associated with said key when thrown in the opposite direction to establish a talking circuit between said cenestablishing a tell-tale circuit OVQI a part of said substation battery circuit and through the operators talking circuit and including a buzzer whereby when the operator replaces the receiver on its hook switch the buzzer will operate until said switch key is restored to normal.

GUSTAV F. C. BAUER.

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