US2449391A - Bidirectional selective remote control system - Google Patents

Description

Sept. 14, 1948. KQGANE 2,449,391

BIDIRECTIONAL SELECTIVE REMOTE CONTROL SYSTEM Filed Jan. 21. 1948 10-51 mm l0 7 mi] FILTERS f F' f F p F F A u A M STATION A MIXERS M, (M

OSCILLATORS F, O, 1 F 0 A F3 03 AL F4 04 n I l k- -l/a s 8 s l 3 5 v v S7 OSCILLATORS F5 05 06 F35 08 STATION 8. MIXERS -1 LMG M, L M

' Y W f FILTERS f F r F f F f F' Inventor":

.Lon Kogan e,

by MAM His Attorney.

Patented Sept; 14, 1948 BIDIRECTIONAL SELECTIVE itEMOTE CONTROL SYSTEM Leon Kogane, Paris, France, assignor to General Electric Company, a corporation of New York Application January 21, 1948, Serial No. 3,464 In France June 22, 1945 Section 1, Public Law 690, August 8, 1946 Patent expires June 22, 1965 1 2 Claims. 1

My invention relates to a frequency selective remote control system which may utilize either wire lines or a space radio channel and which permits simultaneous transmission of one or more control signals in either direction.

A system embodying the invention may comprise two spaced control stations with generators,

at each station for generating a plurality of control frequency signals. These signals may be impressed in any combination on a common bidirectional signal channel interconnecting the stations.

Apparatus is then provided so that for each signal supplied from one station a selected control operation takes place at the other station and without any interference with other control operations performed simultaneously in the same or oppositedirection. An important feature of the invention resides in the fact'that a common beat frequency is utilized to efiect all the control operations and therefore the controlled apparatus at each station may include many identical components.

It is therefore a mainobject of my invention to provide an improved bidirectional remote control system which permits a plurality of selective control operations to be effected either sequentially or simultaneously without any possibility of interference.

It is a further object of my invention to provide an improved frequency selective remote control system which is simple and inexpensive and requires a minimum of components.

For additional objects and advantages, and for a better understanding of the invention, attention is now directed to'the following description and accompanying drawings, and also to the appended claims in which the features of the invention believed to be novel are particularly pointed out.

The single figure of the drawing is a simplified schematic diagram of a remote control system embodying the invention.

Referring to the drawing, the system is illustrated as comprising two separate stations, station A and station E. The two stations are very similar and corresponding elements have been indicated by corresponding reference letters and numerals.

I Station A includes a plurality of oscillation generators. While any desired number may be utilized, it is represented as comprising four oscillators O1O4 whose output frequencies are l b-F4, respectively. Each of the oscillator outputs is supplied to one input of a frequency converter or Mixer Ml-M, respectively Each of the mixer outputs is supplied through a filter F to any 2 suitable control device, represented conventionally as a relay Ill. All of the filter networks may be identical and tuned to pass the same frequency f, and likewise all of the control devices l0 may be identical if desired. The second input to each of the mixers is supplied from av common signal transmission channel ll interconnecting the two stations. The dashed connection Ila is used to indicate schematically that the interconnection may be made either by means of wire lines or by a two-way space radio channel. The output of each of the oscillators Oi-O4 may also be selectively impressed upon the common transmission chan-- gel bg closing a corresponding switch in the groups The elements of station B are practically identical in their arrangement to the elements of station A. It includes the same number of oscillators 05*08, together with corresponding mixers 1'VI]cMa and output filters F and control devices quencies Ft-Fa, may likewise be selectively supplied to the common transmission channel ll through operation of switches -38.

It will be understood that each of the oscillators OlOB may be of any suitable construction known to the art. The mixers Ml-Mii may likewise comprise any suitable known forms of electron discharge device circuits, dry-rectifier bridges, or the like. For reasons that will shortly appear, the filters F are preferably resonant networks each adapted to pass frequency f and having a medium quality factor, or Q.

In the illustrated embodiment of the invention, the four oscillator frequencies at each station are different from each other and also different from the frequency f to which the filters are tuned. Therefore, these frequencies are not transmitted through the filters at the same station and do not actuate the control devices ID at that station. Furthermore, the oscillator frequencies are so selected that one beat frequency produced by combining F1 with F5, F2 with F6, F3 with P1, and F4 with Fe in each case is equal to I. For example, in one suitable form, the relationships may be:

F1Fs:f FaF'1=f F2Fe=f F4-Fs:j

As a further condition, the beat frequencies resulting from combining any one oscillator frequency at one station with any other oscillator frequency at either station must be such as to include only one combination that results in the filter frequency f, and that must be produced in The outputs of oscillators 05-08, at fre-' 3 combination with an oscillator frequency at the opposite station.

The application of these principles and the operation of the system will be more easily understood by reference to a specific example. For instance, assume that the frequencies of the eight oscillators in the drawing are as follows:

Cycles per second F1 800 F: 1200 F2=' 900 Fs=1300 F =1000 F1=1400 F4=1100 Fa=1500 opposite station will be actuated. For example,

if Si is closed, an 800 C. P. S. signal is impressed upon all of the mixers through the common transmission channel. However, only at the mixer M5 will an output at the difference frequency of 400 cycles be produced, actuating the.

associated control device 10. Inspection will show that a similar result follows when any one or more switches at either station are closed.

In the example selected for illustration it will be observed that the beat frequencies produced at the outputs of the various mixers have a frequency separation in all cases of at least 100 C. P. S. If the filters each comprise a simple resonant circuit tuned to 400 C. P. S., the closest frequency to be rejected will have a divergence of at least 100 C. P. S., corresponding to a detuning of 25%. If.the filter has a medium value of Q of at least 50, the attenuation of the closest undesired signal will then be of the order of 25. It is of course desirable not to use filters of too high a Q in order to permit the use of oscillators whose frequencies may vary slightly. For a gain variation of not more than 3 decibels, the effective pass band 2A is equal to f/Q. In the example arbitrarily selected for illustration, this is a pass band of about 400/50, or approximately 8 C. P. S. For the highest local frequency uti lized in the above example (i. e. 1500 C. P. 8.), this permits a variation in oscillator frequency of about 0.5% which is easily secured in ordinary oscillator design.

Inspection will show that it would be possible, if desired, to utilize sum frequencies rather than difference frequencies for control purposes, but in general the difference frequency is to be preferred since it reduces the range of frequencies which the transmission channel must be designed to convey.

The frequency relationships utilized in the practice of the present invention may again be summarized briefly as follows:

(1) All of the oscillator frequencies at any one station must be diflerent from each other and'from the filter pass frequency.

(2) The oscillator frequencies must also be so selected that the beat frequencies produced by combining any selected oscillator frequencyat one station with any other oscillator frequency at either station include only one combination at the selected beat frequency, and that combination must result with an oscillator frequency at the opposite station.

(3) To utilize all the oscillators at each station, there must be as many combinations pro- 4 duced at the desired beat frequency as there are oscillators at each station.

While a specific embodiment has been shown and described, it will of course be understood that various modifications may be made without departing from the invention. claims are therefore intended to cover any such modifications within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A bi-directional selective remote control system comprising a pair of separated control stations, a plurality of oscillation generators at one station, a corresponding number of oscillation generators at the other station, the frequencies of the generators at each station differing from each .other and from a selected beat frequency, said frequencies being so selected that the beat frequencies produced by combining any selected generator frequency at one station with any other generator frequency at either station include only one combination at said selected beat frequency and that with a generator frequency at the other station, a corresponding number of frequency converters at, each station each having one input connected to a common signal transmission channel interconnecting said stations and a second input energized from a respective generator, a frequencyselective control circuit connected to the output of each of said converters, said circuit being adapted to respond to said selected beat frequency and substantially to attenuate other beat frequencies, and switching means for selectively impressing any one or more of said generator frequencies upon said common channel.

2. A bi-directional selective remote control system comprising .a pair of separated control stations, a plurality of oscillators at one station, a corresponding number of oscillators at the other station, the frequencies of the oscillators at each station differing from each other and from a selected difference frequency, said frequencies being so selected that the difference frequencies produced by combining any selected oscillator frequency at one station with any other oscillator frequency at either station include only one combination at said selected difference frequency and that with an oscillator frequency at the other station, there being as many pairs of such combinations producing said selected difierence frequency as the number of oscillators at each station, a corresponding number of mixers at each station each having two inputs and an output, one input of each mixer being supplied from a common signal transmission channel interconnecting said stations, said channel being capable of transmitting all said generator and difference frequencies in either direction,

the other input of each mixer being supplied from a respective oscillator, a control circuit connected to the output of each mixer, each control circuit including a filter tuned to pass only said selected difference frequency Without substantial attenuation, and switching means for selectively impressing any one or more of said oscillator frequencies on said one input of all said mixers simultaneously through said common channel.

LEON KOGANE.

The apppended

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