US2696524A - Automatic fire and burglar alarm system for telephone subscribers - Google Patents

Description

R. D. HUNTINGTON. JR.. Erm. 2,696,524 AUTOMATIC FIRE AND BURGLAR ALARM SYSTEM F OR 4TELEPHONE suBscRIBBRs 2 Sheets-Sheet l I u uentons Rass D. Hunfvgfomdr. .l0/m M. W/'l/l'ams .N .Sk

Dec. 7, l 954 Filed Dec. 25, 1949 Dec. 7, 1954 R. D. HUNTINGTON, JR., Erm. 2,696,524 AUTOMATIC FIRE AND BURGLAR ALARM SYSTEM FOR TELEPHONE SUBSCRIBERS Filed D60. 23, $949 2 Sheets-Sheet 2 BAZTERY C24/ram. OFT/CE RECEIVER TRA/VSM! T TER I n ventola;

Rass 0. Hunf/hgfomw: John M. W/'l//ams Q :#70 By ma//a/mym A switchboard generally indicated by reference numeral 50 is provided at the central station and comprises two alarm lights 52 and 54 for each subscriber and a test jack 56. The lamps 52 and 54 are connected in parallel so as to insure a signal should one lamp fail. The solenoid buzzer 58 is also provided to operate when any receiver unit records an alarm condition. The buzzer may be common to all receiver units or one may be furnished for each one, as desired.

The test jack S6 allows the transmitters output signal to be fed through plug 60 into any receiver unit. lf any receiver should indicate any alarm condition it can be verified by plugging plug 60 into jack 56; and if the lights go out and the buzzer stops the alarm originally indicated in authentic, and not a possible receiver failure.

Condenser 62 is provided for two purposes. The first is to keep the normal direct current of the telephone system from being shunted to ground and causing a trouble condition on the subscribers telephone. The second purpose is to keep the normal ringing current for the subscribers bell from being shunted to ground also. This is accomplished by using a capacitor of a reactance value high enough to keep the twenty cycle ringing current from seeking a ground through condenser 62, in` stead of the low reactance path of the subscribers ringer circuit. The frequency of the transmitters output is very high relative to that of the ringing current utilized and therefore condenser 62 will offer low resistance or reactance to the flow of transmitter carrier current.

Bimetallic or other thermally operated switches 64 (Figures 3-5) are positioned as desired b v the subscriber to the alarm service in the locations he desires, and any one of these switches will open by the application of heat. The nature and location of the switches is determined by the specific conditions providing at the premises to bc protected. Additionally, photo-electrically operated switches 66 may be used in lieu of the thermally operated switches 64. The thermally operated switches or the photo-electrically operated switches are connected across the negative side of the telephone subscribers line and are grounded as shown at 68 or 70 (Figures 3 5). Only one service. either fire or burglar, may be used at one time. But the other side of the subscribers tele phone circuit could be treated as the one previously mentioned. Moreover, two systems could be used on the same yside of the line at the same time by the use of different frenuencies, and filters to keep the fire and burglar signals separated as they pass through either respective control switches. Crystal controlled transn mitters would be essential to this application.

The alarm system is actuated by the carrier frequency current from the transmitter 32 passing` through the output transformer 36 (Figure 2) and through the input transformer or the receiver unit, the alarm relay 42 (Fig. ure 2 being held in an open position while carrier current fiows in a continuous circuit. The signal ows through condenser 62 and is directed to the subscribers line. Means are provided in the telephone circuit. which keep the carrier alarm current in its proper path by preventing it from reaching a false ground in the telephone office. These means in no way hinder the normal usage of the telephone but serve only to keep the alarm signal in the alarm circuit. Thus the alarm signal is directed through the alarm switches 64 or 66 to the ground 68 or 70 and thence back to the transmitter through the ground 34 (Figures 3 5). With this circuit complete, the alarm relay 42 (Figure 2) is held in an open or inoperative condition and the lights 52 and 54 and the buzzer 58 on the control board 50 are not actu ated. Should any of the alarm control switches 64 or 66 open the circuit, the current through the receiver input is interrupted and the alarm relay 42 will drop its armature allowing contacts 72 to close which completes a circuit through battery 74 to the lights 52 and 54 and the buzzer 58. The attendant at the control board 50 manually takes the plug 60 which is powered by the transmitters transformer 36 and plugs it into the jack 56 associated with the lighted lamps 52 and 54. lf the lamps go out it is an indication that the subscribers receiver unit is functioning normally and that the alarm is authentic. From a number stenciled on the face of the lamp, the attendant notifies lthe fire company or the police department, calls the party where the alarm originated, and arranges to have the subscribers line tested by telephone company personnel for any unusual trouble conditions.

The means for preventing passage of the alarm signal to the ground are best shown in Figures 3 through 5 and perform the same function in each case. As shown in Figure 4, the alarm signal is kept from reaching a false ground by the transmitter frequency choke 76. The choke 76 is placed directly in the ground lead of the telephone signal battery and is capable of passing all of the current of the normal telephone signal load. The inductance of the choke 76 if of a value which will attenuate the carrier signal but will not affect the normal telephone operation.

Referring now to Figure 3, it will be seen that the means used comprises chokes 78 and 80 which are inserted directly into the subscribers line at his station and at the central station. The chokes 78 and 80 thus isolate a section of the subscribers line and the alarm circuit must be completed through the switches 64 or 66 or both.

ln Figure 5, there is shown the application of transmitter frequency rejection lters 82 and 84 which are so placed as to insure passage through the burglar or fire alarm switches. The frequency rejection filters 82 and 84 are tuned to the same frequency as the transmitter 10. When a signal from the transmitter attempts to pass through either unit 82 or 84, they offer a very high resistance and force the signal through the alarm circuit.

Obviously the transmitter can be a crystal controlled unit for absolute frequency stability. Furthermore it is within the contemplation of this invention to use the alarm signal for call reminder circuits actuated by clock mechanisms opening the alarm circuit. Additionally, it is within the contemplation of the invention to use transistors to replace any of the vacuum tubes or circuit operations. The device may be used equally well to provide practical protection for homes, ofiices, factories, warehouses or any location which can be served by a main line telephone service. Hotels could use the device to protect each room or utilize a unit to protect a group of rooms which would sectionalize any fire condition immediately. The alarm system as shown is designed to serve only main line subscribers, though systems with different frequencies and tune units could be used on party line service.y

Since numerous modifications will readily occur to those skilled in the art after a consideration of a foregoing specfication and accompanying drawings, it is not intended to limit the invention to the precise embodiment shown and described, but all suitable modifications of this telephonic alarm system may be resorted to which fall within the scope of the appended claims.

Having described the invention, what is claimed as new 1s:

l. For connection to a telephone system having a central station, a customers substation and a telephone line extending between the central station and the customers substation, at least one side of said telephone line being insulated from ground, a signalling system comprising a transmitter including a relatively high frequency wave generator and an output transformer, said output transformer having a ground terminal and an output terminal, a receiving station located in said central station, said receiving station including a receiving transformer including a primary winding and a relay responsive to current flow in said receiving transformer, a coupling capacitor, circuit means including said primary winding of said receiving transformer and said coupling capacitor in series circuit relation for connecting the output terminal of said output transformer to the insulated side of said telephone line, signal switches located adjacent to the customers substation, circuit means including a coupling capacitor connecting said signal switches to said insulated side of said telephone line, and a ground return circuit between said switches and the ground terminal of said output transformer.

2. For connection to a telephone system having a central station, a subscribers substation and a telephone line extending between said central station and said substation, at least one side of said telephone line being ungrounded, a signalling system comprising a transmitter, said transmitter including a signal frequency generator and an output transformer including a primary and a secondary winding, said primary winding being connected to said generator, the secondary winding of said output transformer including a ground terminal and an output terminal, a receiving station, said receiving station including a receiving transformer including a primary and a secondary winding, a relay connected across said secondary winding of said receiving transformer whereby said relay is responsive to current flow in the primary winding of said receiving transformer, a coupling capacitor, a transmitting circuit including said receiving transformer and the primary winding of said coupling capacitor connected in series circuit relation for connecting the output terminal of said output transformer to said ungrounded side of said telephone line, signal switches in proximity with said substation, a second coupling capacitor, a signal control circuit including said signal switches and said second coupling capacitor connected in series circuit relation with said ungrounded side of said telephone line and a return circuit between said signal control circuit and the ground terminal of said output transformer.

3. For connection to a telephone system having a central station, a subscribers substation and a telephone line extending between said central station and said substation, at least one side of said telephone line being ungrounded, a signalling system comprising a transmitter,

said transmitter including a signal frequency generator f and an output transformer including a primary winding connected to said generator, said output transformer including a secondary winding having a ground terminal and an output terminal, a receiving station, said receiving station including a receiving transformer including a primary and a secondary winding, a relay connected across the secondary winding of said receiving transformer whereby said relay is responsive to current flow in the primary winding of said receiving transformer, a coupling capacitor, a transmitting circuit including the primary winding of said receiving transformer and said coupling capacitor connected in series circuit relation for connecting the output terminal of said output transformer to said ungrounded side of said telephone line, signal switches in proximity with said substation, a second coupling capacitor, a signal control circuit including said signal switches and said second coupling capacitor connected in series circuit relation with said ungrounded side of said telephone line and a return circuit between said signal control circuit and the ground terminal of said output transformer, a signal device and a circuit including said relay for energizing said signal device.

4. For connection to a telephone system having a central station, a subscribers substation and a telephone line extending between said central station and said substation, at least one side of said telephone line being ungrounded, a signalling system comprising a transmitter, said transmitter including a signal frequency generator and an output transformer, including a primary and a secondary winding, said primary winding being connected to said generator, the secondary winding of said output transformer including an output terminal, a receiving station, said receiving station including a receiving transformer, said receiving transformer including a primary and a secondary winding, a relay connected across said receiving transformer secondary winding whereby said relay is responsive to current ow in the primary winding of said receiving transformer, a coupling capacitor, a transmitting circuit including the primary winding of said receiving transformer and said coupling capacitor connected in series circuit relation for connecting the output terminal of said output transformer to said ungrounded side of said telephone line, signal switches in proximity with said substation, a second coupling capacitor, a signal control circuit including said signal switches and said second coupling capacitor connected in series circuit relation with said ungrounded side of said telephone line and a return circuit between said signal control circuit and the ground terminal of said output transformer, a signal device and a circuit including said relay for energizing said signal device, an impedance matching pad connected in the series circuit between said output transformer and said telephone line.

5 For connection to a telephone system having a central station, a subscribers substation and a telephone line extending between said central station and said substation, at least one side of said telephone line being ungrounded, a signalling system comprising a transmitter,

said transmitter including a signal frequency generator and an output transformer, said transformer including a primary and a secondary winding, said primary winding being connected to said generator, the secondary winding of said output transformer including a ground terminal and an output terminal, a receiving station, said receiving station including a receiving transformer, said receiving transformer including a primary and a secondary winding, a relay connected across the secondary winding of said receiving transformer whereby said relay is responsive to current ow in the primary winding of said receiving transformer, a coupling capacitor, a transmitting circuit including the primary winding of said receiving transformer and said coupling capacitor connected in series circuit relation for connecting the output terminal of said output transformer to said ungrounded side of said telephone line, signal switches in proximity with said substation, a second coupling capacitor, a signal control circuit including said signal switches and said second coupling capacitor connected in series circuit relation with said ungrounded side of said telephone line and a return circuit between said signal control circuit and ground terminal of said output transformer, a signal device, a circuit including said relay for energizing said signal device, an impedance matching pad connected in the series circuit between said output transformer and said telephone line, chokes inserted between said transmitting circuit and said central station and between said signal control circuit and said substation.

6. For connection to a telephone system having a central station, a subscribers substation and a telephone line extending between said central station and said substation, at least one side of said telephone line being ungrounded, a signalling system comprising a transmitter, said transmitter including a signal frequency generator and an output transformer including a primary winding connected to said generator, said output transformer including a secondary winding having a ground terminal and an output terminal, a receiving station, said receiving station including a receiving transformer, said receiving transformer including a primary and a secondary Winding, a relay connected across the secondary winding of said receiving transformer whereby said relay is responsive to current flow in the primary winding of said receiving transformer, a coupling capacitor, a transmitting circuit including the primary winding of said receiving transformer and said coupling capacitor connected in series circuit relation for connecting the output terminal of said output transformer to said ungrounded side of said telephone line, signal switches in proximity with said substation, a second coupling capacitor, a signal control circuit including said signal switches and said second coupling capacitor connected in series circuit relation with said ungrounded side of said telephone line and a return circuit between said signal control circuit and the ground terminal of said output transformer, a signal device, a circuit including said relay for energizing said signal device, an impedance matching pad connected in the series circuit between said output transformer and said telephone line, chokes inserted between said transmitting circuit and said central station and between said signal control circuit and said substation, an auxiliary circuit for directly connecting said receiving transformer across said output transformer.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 666,883 Kitsee Ian. 29, 1901 1,810,739 Vedder June 16, 1931 2,080,136 Johnson May 11, 1937 2,185,361 Towne Jan. 2, 1940 2,279,394 Fountain Apr. 14, 1942 2,279,739 Lurie Apr. `14, 1942 2,331,391 Hague Oct. 12, 1943 2,439,502 Tate Apr. 13, 1948 2,568,342 Koehler etal Sept. 18, 1951 FOREIGN PATENTS Number Country Date 620,158 Great Britain Mar. 21, 1949

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