Title:
Photoelectric controlled oscillator device
United States Patent 2312127


Abstract:
My present invention relates to oscillators controlled by photo-electric devices, and more particularly to alarm systems utilizing light-controlled oscillator circuits for generating a signal wave capable of being detected -t a point remote from the oscillator, One of the main objects of my...



Inventors:
Shepard Jr., Francis H.
Application Number:
US30319139A
Publication Date:
02/23/1943
Filing Date:
11/07/1939
Assignee:
RCA CORP
Primary Class:
Other Classes:
250/214R, 331/66, 340/538, 340/538.17, 340/555, 340/562
International Classes:
G08B13/183
View Patent Images:



Description:

My present invention relates to oscillators controlled by photo-electric devices, and more particularly to alarm systems utilizing light-controlled oscillator circuits for generating a signal wave capable of being detected -t a point remote from the oscillator, One of the main objects of my invention is to provide an alarm system in which capacity and photo-electric units may be plugged into the nearest alternating current outlets of a power line, and made to place a signal wave on the power line on the approach of an intruder whereby a large residence, store, warehouse or office building can be protected without the necessity of costly installation wiring costs.

Another important object of this invention is to provide a signalling system wherein a lightcontrolled oscillator is connected to a power line for energization, and the power line functioning as a wave transmission line as well; one or more signal wave indicator devices being plugged into the same power line at convenient places remote from the oscillator.

Another object of my present invention is to prTvide burglar alarm systems which dispense 25, with the need for expensive wiring installations, and wherein the signalling device is a photo-electrically controlled oscillator which is plugged into the existing power line; a simple one-tube relay alarm circuit being plugged into the power line at any desirable remote point to indicate the signal oscillations transmitted over the power line.

Still other objects of this invention are to improve generally the simplicity and efficiency of burglar alarm systems, and more especially to piovlde an alarm system which is not only durable and reliable in operation, but is economical to manufacture and install, The novel features which I believe to be charadteristic of my invention are set forth in particularity in the appended claims; the invention itself, however, as to both its organization and method of operation will best be understood by reference to the following description taken in connection with the drawing in which I have indieated diagrammatically a circuit organization whereby my invention may be carried into effect.

Referring now to the accompanying drawing, there is shown a power line I which is to be understood as transmitting 60 cycle current through a structure such as a large residence, a store, warehouse or an office building. Assume that the room, or area, where socket 2 is located is to be,protected against intruders. There is, then, plugged into the socket 2 the prongs of a plug S 56 which functions to provide the means for feeding energizing current to the tubes of the oscillator, and which also acts to transmit the signalling oscillations to the power line I for transmission to one or more remote points. The light-controlled oscillator comprises an oscillator tube 4 which may be of the 25A6G type. This type of tube may be a .pentode employing an indirectly heated cathode. The tube 4 includes the anode 5, cathode 6, control grid 7, intermediate grid 8 and sup"pressor grid 9. Both the heater filament 10 and cathode 6 are tied to the lead II which is connected to one terminal of the plug 3.

The plate 5 is connected to the other terminal of plug 3 through a path including coil 12 and lead 13. The grid 8 is tied to the lead 13, while grid 9 is tied to the cathode 6. The coil 14 connects cathode 6 to the control grid 7 through blocking condenser 15. The adjustable condenser 16 connects the coils 14 and 12 in series, and acts to resonate the oscillator to the operating frequency desired for the signal waves to be transmitted over power line I. Coils 12 and 14 are strongly coupled by the condenser 16.

The tube 17, which may be a pentode of the 6J7 type, acts as an amplifier for the output voltage of the photo-electric tube 18. The latter may be a phototube of the 922 type, for example. Tubes 17 and 4 are connected back to back; the potential of plate 27 is negative with respect to line II and hence is used to bias the grid 7 of oscillator 4. The anode 19 of the phototube is connected to lead I1. The cathode 20 is connected to a movable tap 21, the latter being adjustable along 35. cathode resistor 22, through resistor 23 and condenser 24 arranged in series. Condenser 24 increases the sensitivity of the device, and eliminates instability due to contact potential variations. The cathode end of resistor 23 is connected by lead 25 to the control grid 26 of amplifier 17. The plate 27 is connected through resistor 28 to lead I , condenser 29 by-passing the resistor.

The anode end of resistor 28 is connected by resistor 30 to grid 7. The screen grid of tube 17 is connected by slider 31 to any desired point on resistor 32. The latter is included in series with the heater elements 33 and A0. The cathode 34 is tied to filament 33, and the latter is connected to lead 13. The condenser 35 by-passes that por50. tion of resistor 32 between tap 31 and cathode 34, ' while condenser 36 by-passes the cathode resistor 22.

There is provided a light source 40 which projects a beam of light 41 upon the cathode 20 of photo-electric tube 18. The tap 21 is adjusted along resistor 22 towards the bottom thereof with light on the cathode 20. The tap 21 is now moved towards the top thereof past the point at which the oscillator 4 is prevented from oscillating. If, now, any obstacle is placed between the light source 40 and the phototube 18 which cuts off the light beam 41, oscillations will again commence.

These oscillations, or waves, are impressed upon the power line 1, and transmitted over the power line. At a remote room, or area, there is located any desired type of detector 50 followed by a relay device 61, the latter operating any desired indicator 52. It will, therefore, be understood that the rectangle designated 60 represents a remote location at which point an indicator or alarm device is connected to the power line to respond to the oscillations transmitted over the line. The detector may consist of a single tube connected to function as the usual detector of unmodulated carrier waves, and the relay and indicator device can be of any well known construction. The indicator 62 itself can be of the audible or visible types. It is, also, shown in the drawing that the power line may have coupled thereto another detection and relay unit 10. Of course, as many remote alarm devices as is desired may be utilized in conjunction with the power line.

Considering more specifically the function of the light-controlled oscillator network, it is first pointed out that the condenser 16 may be adjusted so that the oscillator tube will produce oscillations of any desired frequency that will pass over the power line. It is to be understood that the frequencies may be in the audio or radio ranges. In general, when the beam of light 41 is interrupted by an intruder or obstruction the alternating current bias on the grid 26 of the amplifier tube II cuts off the plate current of the tube. This causes the voltage drop across the plate load resistor 28 to decrease thereby removing the negative voltage from the grid 7 of the oscillator tube. Such removal of negative voltage allows the oscillator to commence oscillating, and the oscillator voltage is impressed upon the power line through the oscillator tank circuit which is series resonant with the line.

The s6tting of the tap 21 determines the effective bias on the tube IT in two ways. On the negative part of the alternating current cycle the condenser 24 tends to charge up by drawing grid current to the peak voltage between cathode 34 and the setting of tap 21. On the active positive half-cycle the voltage on the grid is equal to the voltage across the condenser due to that condenser charge plus the alternating current voltage applied through the condenser from resistor 22 minus the drop in the resistor 23 determined by the amount of light on phototube 18. Thus, when there is plenty of light on the phototube the grid 26 is effectively above cut-off, and the tube I7 draws plate current thereby charging the condenser 25 negative.

This negative voltage cuts off the oscillator tube through the path including resistor 3S, and thus no oscillation pulses are put on the power line.

When the light 41 is cut off the grid 26 goes effectively more negative, and the plate 27 becomes less negative. This allows the oscillator tube 4 to oscillate, and causes the oscillation pulses to be impressed on the power line. Tube rf. operates as an alternating current operated direct current amplifier, and also as a gridcontrolled alternating current rectifier.

By connecting the shell of tube I7 and the condensers 35 and 36 as shown, and by shielding the grid wires of tube IT, a "back-lash" effect is eliminated. This latter effect is due to a radio frequency feedback to the tube I1. With "backlash" effect eliminated, and a fairly stable power line, the circuit will operate satisfactorily for small light changes. If the line has large voltage variations it is wise to make the circuit Insensitive to small light changes. This is normally easily provided for in relay operation. If high light intensities are used (more than 0.1 lumen) the cathode of tube I1 and the upper end of resistor 22 should be returned to a higher point - on resistor 32. The indicator 52 can be in the form of a light, floodlight, bell, a siren, an annunciator, or any other well known device.

The following constants are given for the oscillator network by way of illustration, and it is to be clearly understood that these figures are in no way restrictive: Ra-10 megohms Ra-- megohm Rn-10,000-50,000 ohms RM-0.5 megohm C-4-0.001 microfarad (mf.) C-O0.1 mf.

CU-0.01 mf.

Cxa-0.01 mf.

Cis-25 mmf.

While I have indicated and described a system for carrying my ,invention into effect, it will be appaarent to one skilled in the art that my invention is by no means limited to the particular 85 organization shown and described, but that many modifications may be made without departing from the scope of my invention, as set forth in the appended claims.

What I claim is: 1. In combination with an alternating current power line, an oscillator network, light-responsive means for normally preventing oscillation production by said network, means for connecting said network to said power line for energisation of the network with alternating current from said line, means for coupling said network in oscillation energy transfer relation to said line whereby the line functions as the transmission medium for the oscillations, means connected to said power line at a point remote from said network for indicating oscillations transmitted over said line from said network, said light-responsive means including a light source, a phototube having light from said source im85 pressed thereon, and a tube energized by said power line and responsive to current flow through said phototube for rendering said oscillator network inoperative.

2. In combination with an alternating current power line, an oscillator network, light-responsive means for normally preventing oscillation production by said network, means for connecting said network to said power line for energization of the network from said line, means for 05 coupling said network in oscillation energy transfer relation to said line whereby the line functions as the transmission medium for the oscillations, means connected to said power line at a point remote from said network for indicating oscillations transmitted over said line from said network, said oscillator network including a tube having input and output electrodes coupled to provide said oscillations, a second tube having an output circuit arranged T7 to control the potential difference between said oscillator tube input electrodes, said energization means applying alternating current from said line to both said tubes to energize them, and said light-responsive means including an element for controlling the conductivity of said second tube.

3. In combination with an alternating current power line, an oscillator network, light-responsive means for normally preventing oscillation production by said network, means for connecting said network to said power line for energization of the network with alternating current from the line, means for applying said oscillations to said line whereby the latter acts as a transmission line for the oscillations, means connected to said power line at a point remote from said network for indicating oscillations transmitted over said line from said network, said oscillator network including a tube having input and output electrodes coupled to provide oscillations of a predetermined frequency, a second tube having an output resistive impedance arranged in its space current path, means to apply voltage developed across said impedance to said oscillator tube input electrodes in a cutoff sense, said second tube including a control electrode, said light-responsive means including a photo-electric tube having a control connection to said control electrode such that space current flows normally through said resistive impedance.

4. In combination with an alternating current power line, an oscillator network, lightresponsive means for normally preventing oscillation production by said network, means for connecting said network to said power line for energization of the network with alternating current from the line, means for applying said oscillations to said line whereby the latter acts as a transmission line for the oscillations, means connected to said power line at a point remote from said network for indicating oscillations transmitted over said line from said network, said oscillator network including a tube having input and output electrodes coupled to provide oscillations of a predetermined frequency, a second tube having an output resistive impedance arranged in its space current'path, means to apply voltage developed across said impedance to said oscillator tube input electrodes in a cut-off sense, said second tube including a control electrode, said light-responsive means including a photo-electric tube having a control connection to said control electrode such that space current flows normally through said resistive impedance, and connections from said line to the electrodes of each of said oscillator tube, second tube and photo-electric tube thereby to energize them with said alternating current.

FRANCIS H. SHEPARD, JR.