US3103611A

US3103611A - hooper

Info

Publication number: US3103611A
Authority: US
Publication date: 1963-09-10
Anticipated expiration: 1980-09-10

Description

Sept. 10, 1963 B. E. HooPER 3,103,611

SIGNALLING SYSTEM Filed Jan. 7, 1958 Sept. 10, 1963 5.12. HooPER SIGNALLING SYSTEM 5 Sheets-Sheet 2 Filed Jan. 7, 1958 United States Patent O 3,103,611 SIGNALLING SYSTEM Brian E. Hooper, Sherman Oaks, Calif., assigner to Packard-Bell Electronics Corporation, Los Angeles, Calif., a corporation of California Filed Jan. 7, 1958, Ser. No. 707,603

12 Claims. (Cl. 317-147) This invention relates to apparatus for remotely controlling the operation of a distant mechanism. More particularly, the invention relates to apparatus for ytransmitting signals in a particular code from an auto-mobile toward a `garage and tor receiving the signals at the lgarage tocontrol the opening and clos-ing of a door in the zgarage.

In this advancing age of automation, equipment is constantly being invented and developed -to simplify ,the tasks of men and women. lFor example, apparatus is now being used to transmit signals from an automobile as the automobile approaches a garage so that the garage door can be opened without any necessity for the driver to -get out of the car. Similarly, the apparatus can be operated to close a garage door ,after the automobile has left the garage. This apparatus has been especially desirable in inclement or cold weather and has been particularly useful to Women drivers at night.

Remote control equipment for operating `garage doors has been steadily increasing in popularity. This increase in popularity has presented certain problems. One probh lem 'has resulted from thefact that all ot the manufacturers are allowed only a few transmitting frequencies by governmental authorities such as the Federal Communications Commission. When a number of different installations are made by dierent manufacturers in a particular area, it may sometimes occur that a car ap proaching a particulary garage may open the door for that garage as well as the door for other garages near the particular garage. This may result from Ithe fact that the particular garage may have an installation of one manfacturer, while other garages in the area may have an installation of other manufacturers. For this reason, it has become necessary to dierentiate between installations in a neighborhood even though such dfilierent-iation has been made diicult by the use of a single carrier frequency Itor the transmitted Isignal-s.

Various attempts have been made to :encode the carrier signals with individual and particular platterns to distinguish each installation from the others. These attempts have not been entirely successful ir'rom an operational standpoint since each gavage mstallation has not been entirely independent in operation from all of the other garbage installations in the neighborhood. Furthermore, the equipment resulting 'om such attempts has been eX- pensive .in spite oct the incomplete success from an openational standpoint. This invention provides a system tor overcoming the above disadvantages and at the same time providing equipment of reduced cost.

Dhe system constituting this invention produces 'a carrier signal lof the frequency specified by the governmental authorities. This carrier `signal is alternately modulated on a time-sharing basis by signals ot a relatively low frequency rand second signals of a relatively high frequency. Each of the low frequencies and high frequencies can be adjusted for different installations to provide a differentiation between the installations.

For example, one installation may use signals ot 9 kilocycles per second to constitute the llow frequency and signals of 29 kilocycles per second to constitute the high frequency. Another installation may respectively use signals of 11.5 .and 34 kilocycles per second as the low and high frequencies. Similarly, a sthird installation may 3,103,611 Patented Sept. 1G, 1963 ICC 2 use modulating signals of 49 and 34 kilocycles per second on `a timesharing basis. By using circuit-s tuned to the particular trequenciea each installation is able to pass only signals at the particular trequencies selected for that installation. The system is so designed that thel garage door can be opened only when the modulating signals at both the low and high frequencies are able to pass the tuned circuits lat the installation. p

The system constituting this invention utilizes novel techniques to simplify the construction of the system. For example, substantially the same circuitry is used at the transmitter of an automobile to produce the modulating signals of relatively low irequency and the modulating signals of relatively high frequency on a time-sharing basis. At the receiver, novel circuitry is used to actuate the garage door mechanism only when both modulating ,signals of the selected values lat the low and high frequen cies are received concurrently.

Another Iadvantage of the Iappamatus constituting this invention results trom the use of the antenna normally provided on an automobile to receive radio signals as the antenna of transmitting signals to the receiver at the garage door. This is accomplished by shortcircuiting the input to the radio at the time that signals are to be transmitted to the receiver at the :garage door. By slrort-circuiting the input to the radio, the limpedance of the nadio cannot be coupled to fthe antenna to `affect the tuning of the tnansmitted signals. Furthermore, the

v nadio cannot be damaged in :any Way in case of kany considerable intensity in the transmitted signals.

The apparatus constituting this invention |also has certain other advantages. It utilizes a simple mechanism to attach the transmitter under the dashboard of lan auto mobile. This attachment is made in such a Way that the transmitter can be easily lat-tached to the dashboard by fastening one screw land can be easily detached from the dashboard at any time by unliast-cning the screw.

In the drawings:

FIG. 1 is -a diagram of electrical circuitry showing the electrical construction of a transmitter included in one embodiment of the invention;

FIG. 2 is la diagram of electrical circuitry showing the electrical construction of a receiver included with the transmitter shown in FIG. 1 in one embodiment of the invention;

FIG. 3 is la tnagmentary perspective view of the housing for the transmitter shown in FIG. 1 and illustrates the manner in which the transmitter housing may be disposed under the dashboard 'of an automobile;

FIG. 4 is an exploded perspective View of the different members forming the transmitter housing shown in FIG. 3 fand illustrates how the various membems may be connected to one another and to the automobile dashboard;

FIG. 5 is a :fragmentary sectional view illustrating the construction and relative disposition of a push butt-on shown in FIG. 4 and of members associated with the push button including a pair of switches included in the circuit diagram shown in FIG. 1;

FIG. 6 is a chant illustrating possible values lfor modulating signals of low and high frequencies produced on a time-sfharing basis by the transmitter shown in FIG. l;

FIG. 7 is a chant illustrating the possible combinations of modulating signals at the low and high f irequencics and [further illustrating the value of the capacitance which has to be added to obtain the desired combination of modulating frequencies; and y FIG. 8 is a schematic diagram illustrating the diiferent possible connections between pairs of terminals in a connector board shown in iFIG. l to .obtain the production of modulating signals at either high or low frequencies or the production of modulating signals at both high and low frequencies on a time-sharing basis.

.connected to' the movable contact off the vibrator.

mounted in any suitable and convenient manner on an automobile to lsetnd signals toward a Agarage door. The antenna may be similar to those used on automobiles at present to receive signals for operating the radios in the automobiles. The antenna 10 may be used to receive signals ttor introduction to the car radio during the time thaty it is not being used to'obitain the opening or closing of a garage door. The connection tfrom the antenna 10 through a coil 11 tothe input to a radio (not shown) in an automobile is indicated schematically by a cable 12.

A pair of iganged single-pole single-throvv switches 14 e and 16 are included in the transmitter circuitry shown in cal1y-driven vibrator 18. The vibrator 18 may be of any suitable construction such as a type 1601 manufactured by the P. R. Mallory Company. The vibrator 18 'is 'provided with two stationary contacts which will hereafter be designated as the upper and lower stationary cont-acts to conform with the relative positioning olf these contacts itn FIG. l. rPhe movable contact olf the vibrator 1S may b e spring loaded for normal disposition against the lower stationary contact of the vibrator in FIG. 1.

,'Ilhe upper `stationary Contact of the vibrator 18 is connected to one terminal orf an energizing coil 20 included in the vibrator andthe other terminal of the coil 20 is The upper stationary contact of the vibrator 18 also has a common connection with one terminal of the primary winding in a transformer generally indicated at 22. The other :terminal of the primary winding in the transformer '22 is connected to the middle one of three terminals in an adaptable terminal board generally indicated at 24.

A resistance 26 having a suitable valuesuch as approximately 3 `ohms is connected between the left and middleterminals ofthe bcand 24 and a resistance 28 having a suitable Vvalue such as approximately 13 ohms is connected between the left and lright terminals of the board 24. The leit yterminal of the board 24 is connected to one terminal kof a battery 25 in an automobile, the other terminal lor the batte-ry being grounded. Although the left terminal ofthe board 24 is shown as being connected to the positive terminal of the battery 25 in FIG.

l, it can also be connected'as electively to the negative terminal ot the battery. The right terminal of the board 24 is connected to first terminals ccf the tilaments in the vacuum'tubes 'used `in the transmitter, the second terminals orf the i-laments being lgfnounded. Actually, in the embodiment of the transmitter shown in FIG. l, only two tubes are included and both of these tubes may be disposed within a single envelope.

i r[the terminal board 24 and the resistanoes 26 and 28 are included to adapt the transmitter shown in FIG. 1 for operati-on` in automobiles using l6-volt batteries and in automobiles using `l2-vol-t batteries Vsince the new automobiles are now .using l2-volt batteries Whereas the old automobiles have been using 6-volt batteries. When the transmitter shown in lFIG. l is to be enengized from a l2- volt battery, the connections are made as shown in FIG. l and as described above. For operation of fthe transmitter shown in FIG. `1 ifrom a 6-volt battery, the three terminals in the board 24 are short-circuited to one another.

A rectifying stage :generally indicated at 32 is connected across the secondary rwinding .of the transformer 22. Ilhe rectitying stage 32 includes la capacitance 34 which is in parallel with the secondary Winding tout the transformer 22 and which is provided with a suitable value such as approximately 0.01 microlfarad. One terminalof the capacitance 34 is grounded and the other terminal :of the capacitance is connected to the platterot a diode 36, which may be a itype lHW t12575',y mainteV factured bythe Siemens Company :off Germany.. The

cathode Voi? the diode 36 |has a comrnon connection with the iirst terminal of a capacitance 38, the second terminal of lwhich is grounded. The capacitance 38 mayV have a suitable value such as approximately 4 microfarads.

The voltage fon the cathode of the diode 36 is applied to an intermediate tap in a. coil 40. The coil 40` is magnetically coupled to the coil llfto induce signals' in the coil for introduction to the antenna 1%. A capacitance 42 having a suitable value such as approximately Vl0 micromicr'ofarads is in parallel with thecoil 40l to tune the coil to a particular carrier frequency.V The lower terminal of the capacitance 42 in FIGA is connected to a yfirst terminal in a crystal 44 which may be constnucted to provide a. suitable carrier (frequency suchV as approxi; mately 27.12 megacycles. This frequency is assigned by the .Federal Communications Commission. The frequency is the same fior al-l manufacturers regardless of the number of manufacturiers and'rregardless of the nume ber of sets.

The other terminal of the crystal 44 is connected to the control grid off a rtube 46. 'llhe tube 46 may be in-1 eluded with another tube in a single envelope designated as a type 6AN8. When two tubes are included in a single envelope, only one envelope is required in the transmitter, as will be'seen from the subsequent discussion..

A capacitance 45 is connected between the control grid lof the tube 46 and' ground to neutralize any capacitive effects in the crystal `44. rBhe capacitance 45v may be provided with al suitable value such as approximately l0 micromicrofarads. The control grid of the tube 46 is biased by a pair of resistances 48 and 5G connected in series between the control .grid and ground.. The resistances 4S and 50 are respectively provided with suitable values such as approximately 10 kilo-ohms and 22V kiloohr'ns. Y l

The plate of the tube 46 is connected to the upper tergrounded. The screen grid is positively biased from the cathode of the diode 36 through a network formed byV a pair of resistance@` 52 and `55, which are respectively provided kwith suitable values such as approximately 56 kilo-ohms and 3.3 kilo-ohms. A capacitance 54 having a suitablevalue such as approximately 02001 microfarad is connected between the screen grid of the tube 46 and ground.

Signals are applied to the common terminal between the resistances 43 and 50 through a suitable coupling capacitance 5 8 from the plate of a tube 60 which may be included in a common envelope with the tube 46. The plate of the tube 60` is adapted to receive a positive potential through a suitable resistancel 56 from the cathode of the diode 36. The resistance 56 and the coupling capacp itance `58 may respectively have suitable values such as approximately 6.8 kilo-ohms and 0.001 micro'farad.r The cathode of the tube 60 has a common connectionwith one terminal of a resistance 62, the other terminal of which is grounded. The resistance 62 may have a suitable value Lsuch as approximately 2.2 kilo-ohms. cathode of the tube 60 also has a common terminal with an intermediate tap on a tuning coil 64.

A resistance 66 having a suitable value 'such as approximately l0 kilo-ohms extends electrically between the grid of the tube 60 and ground. A capacitance 68 is connected between the grid of the'tube 60 and one end terminal of the tuning coil 64, rthe other end terminal of the tuning coil being grounded. A capacitance 70 having a suitable value such as approximately 220 nn'cromicrofarads is in parallel with the tuning coil 64.

e A capacitance 72` and 'an adjustable tuning capacitance 76 have first terminals connected to the ungrounded end terminal of the tuning coil 64 and have lsecond terminals The connected to an intermediate terminal in a connector board 74. The combined value of the capacitances 72 and 76 is dependent upon the frequencies to be provided for modulating signals of relatively low frequency. The' combined value of the capacitances 72 and 76 for different combinations of low and high frequencies may be seen from a chart `shown in F1GQ7. Variations in the.

combined value may be obtained by adjusting the capacitance 76 or by varying the value of the capacitance 72.

The connector board 74 is provided with left, intermediate and right terminals, and the left terminal is grounded. yTo obtain only modulating signals of relatively high frequency, none of the terminals in the connector board 74 is connected to any of the other terminals in the board. This may be seen from the schematic diagram shown in- FlG. 8i The lett and intermediate terminals in the connector board are connected together to obtain only modulating signals of relatively low frequency. For the production of modulating signals of both low and high frequencies, the intermediate and night terminals in the board 74 are connected together. The different electrical arrangements between the terminals in the board 74 are illustrated in FIG. 8. The dilerent circuit arrangements produced by such connections will be described in detail subsequently.

The receiver shown in FG. 2 is located at the garage door and is designed to receive signals for opening or closing the door. connected in a series circuit to ground with a coil 1012. A coil 104 is magnetically coupled to the coil 102 Vand is in parallel with a capacitance 106 having a suitable value Y such as approximately micromicrofarads. First terminals ofthe coil 104 and the capacitance 106 are grounded. A capacitance '108 and a resistance 110 are in lseries across the coil 104 and the capacitance 106. The capacitance 108 and the resistance 110 may be respectively provided with suitable values such as approximately 100 micromicrofarads and 4.7 kilo-ohms.

The common terminal between the capacitance 108 and the resistance 110 is connected to the control gnid of a tube 41112, the cathode and suppressor grid of which are grounded. The tube 112 may be included with another tube in an envelope designated asa -type 6X8. A capacitance 114 having a suitable value such as approximately .01 microfarad is connected between the screen grid of the tube 1.12 and the ground, A resistance 1161s connected between the screen grid of the tube 112 and a source 123 of direct voltage to apply a limited potential of positive polarity to the `screen grid. A capacitance 118 is connected between the resistance `116 and ground to decouple the positive potential from the source 123 relative to ground. The resistance 1116 may have a suitable value such as approximately 56 kilo-ohms and the capacitance `118 may have a suitable value such as approximately 0.01 microfarad.

A tuned circuit is connected to the plate of the tube 112. The tuned circuit includes a capacitance 120 having a suitable value such as approximately l0 micromicrofarads and also includes the primary winding of a transformer 122. Second terminals of the capacitance 120 and the primary Winding of the transformer 122 are connected to the positive terminal of a source 123 of direct voltage to receive a suitable potential such as approximately +140l volts.

The secondary winding ofthe transformer 122 has one terminal grounded and has the other terminal connected The receiver includes an antenna 100 to the cathode of a diode A124, which may be a type a suitable value such as approximately 10 megohms and is also connected to the grid of a tube 132 which may be included in the same envelope as the itube 112. The cathode of the tube 132 is grounded and the plate of the tube is adapted to receive a positive potential.A This potential is applied from the same terminal of the voltage source 123 as the tuned circuit formed by the capacitance and the primary winding of the transformer 122. This potential is applied to the plate of the tube 132 through a resistance `1311 having a suitable value such as approximately 47 kilo-ohms.

A capacitance 136 is disposed electrically between Ithe plate for the tube 132 and ground. A capacitance 138 and a resistance are in series across the capacitance 136. The capacitance 138 and the resistance 140 may be provided with suitable valu-es such as app-noxiinately 0.101 microfaradand approximately 1 megohrn. The common terminal between ,the capacitance 138 -an-d the resistance 140 is connected to lthe control grid of a tube 142 which may be included with another tube in an envelope designated as type 12AT7. The cath-ode of the Iturbe 142 is grounded.

The plate or" the tube '142 is adapted to receive a posi- .tiv'e potential from lthe Same terminal of the voltage sou-nee 123 as the plate of the tube 132. This potential is applied to Ithe plate `of the tube 142 through a resistance 144 lhaving `a suitable value such a-s approximately 47 kiloiohrns. A coupling capacitance 146 and la resistance 148 are in series `between the plate of the tube 142 and gnound. The capacitance 146 :and the `resistance 148 may be respectively provided with suitable values such as 0.0101 microanad and 470 kilo-ohms. The common lterminal between the capacitance 1416 and the resistance 148 is connected to the control grid of a tube 150 having, its cathode grounded.` The tube 150 may be included in fthe same envelope as the-tube 142.

Th same posit-ive potential is lapplied to the plate of the tube 150 as is applied to vthe plates of the tubes 132 and 142. This potential is applied lthrough a resistance 152l having a Suitable value suchy as :approximately 47 kilo-ohms. One terminal of a coupling capacitance 154 having -a suitable value Isuch as lapproximately 0.01 micnofai-ad is also connected to the plate of the tube 150. The other terminal of the capacitance 154 is connected to the plate of a diode 156 and to the cathode of ya diode 160. The diodes 156 land 160 may be included in a type IRC 9KR22 manufactured by the International Resistance Company. The cathode of the diode 156 is grounded and the plate of the diode 160 is biased at a suitable potential such Ias approximately -2 volts from the voltage source 123. A capacitance 162 having a suitable value such as approximately 0.01 microfarad extends electrical-ly from the plate or the diode 1601to ground.

The second terminal of the capacitance 154 also has common connections with iirst terminals of

oapacitances

166 and 168. A .tuned circuit formed by an adjustable coil 170 yand a capacitance 172 in parallel is connected between the second terminal of the capacitance 166 and ground. Similarly, la tuned circuit formed by an adjustable coil 174 and -a capacitance 176 in parallel is connected between the second terminal :of the capacitance 168 and ground. The second terminals of the

lcapacitances

166 and 168 are also respectively connected to lirst terminals of capacitances and 182, each of which is provided with la suitable value such as approximately 0.001 microlfarad.

Second terminals of the capacitanees 180* and 182 are connected lto the control grids of tubes 184' |and 186 which also respectively connected to'frst terminals of a pair of capacitances 192 and 1.914, each having a suitable value such :as approximately 0.001 microtarad.

The second terminal tot the capacitance 192 has a common connection with the cathode of a diode 1%, the plate of which is connected to the voltage source 123 to receive a suitable negative potential such lasl approximately 7.5 volts. Resistances 19S, 1200 and 202 are in series between the control grid lof the tube 18,4 and the plate of thedifode 196. The resistances 198, 200 `and 202 may be respectively provided with suitable values such as 470 kilo-ohms, 100 kilo-.ohms and 2.2 megohms. llhe common terminal between `the resistanccs 200` and 202 is also connected to the second terminal of the capacitan-ce 192. A capacitance 204 having a suitable value such as 0.01 micnofarad is Iconnected between the plate .of the diode 196 and they common terminalbetween the'resistances 198and 200.`

Similarly, the second .terminal of the capacitance 194 is connected to the cathode of a diode `206, the plate of which is Iadapted to receive the negative potential of approximately -7.S volts from the voltage source 123.

Resistances

208, 210 and 212 are in series between the contnol grid of the tube 186 and the plate of the diode 206. The resistances 2018, 210 `and 212 may be provided Y 214 having a suitable value such :as 0.01 microffanad is connected between the plate of the diode 206iy andy the common terminal between the resistances 208 `and 210.

A relay coil 218 and 'a resistance 220 extend electrically in series from the common terminal between the resistvances 188 and 190 to the terminal in the voltage source 123 lior applying the positive potential of approximately v +140 volts. The resistance 220 may be provided with la suitable value such as approximately 1.5 .kilodohms A capacitance 222 having 'a suitable value such as approximately 50 microfarads is in parallel with the series branch formed by the relay 218 `and the resistance 220.

A switch 224 is magnetically coupled to the coil 218. the switch 224 may be included in apparatus for obtaining the operation of a garage door to either an opened position or `a closed position. For example, the switch may be included-in apparatus disclosed and claimed in U.S. Patent 2,805,059, issued September 13, 1957', to Willard I. Green. 'I'his apparatus is illustrated schematically at 226 in FIG. 2. The lapparatus may include a motor which is connected in a circuit with the switch `224 to become energized upon Ithe 'closure of the switch.

' closed. When the switch. 14 is closed, it grounds the coil 11 and the ungrounded terminal of the cable 12: to prevent radioy signals received by the antenna fnom being introduced to the radio (not shown) in an automobile. Ihis multes the automobile radio so that power from the transmitter shown in FIG. 1 cannot be introduced to the radio. This is desirable to prevent the automobile radio Ifrom being damaged, especially when the power output from the tube 46 is not limited in a manner which will be described in detail subsequently. Furthermore, by grounding the input to the automobile radio, the radio cannot-introduce any reactanceto the antenna 10 and the coil 11 to :affect the operation of the antenna and change the `frequency of response of the coil.

'l'lhe switch 16 becomes closed at the seme time as the switch 14. This grounds the movable contact of fthe vibrator 18. Since the movable contact of the vibrator 18 normally engages the lower stationary contact in FIG. l, a continuous circuit is established which includes the automobile battery 25, the primary winding off the tnansformer 22, the coil Ztl land the stationary and movable contacts of theswitch 1'6. rThis current causes the coil 2@ to become energized so as to actuate the mov-able contact of the vibrator 18 into engagement with the upper stationary contact ofthe vibrator. In this position of the movable contact of the vibrator 18, the ycoil 20 becomes short-circuited. This causes the movable Contact of the vibrator to return to a position engaging the lower stationary contact of the vibrator. ln'this way, the movable contact of the vibrator y1S alternates in engaging the upper and lower stationary contacts ofthe vibrator yat a frequency dependent upon the characteristics of the spring loading of the movable contact.

Current ows through the primary winding of the transformer 22 whether the movable contact Yof the vibrator '1li is engaging the upper or lower stationary contacts of the vibrator. However, in the lower position of the movable contact in the vibrator 18, the coil 2li is included in `a series circuit with the primary winding of the transformer 22, whereas in the upper position of the 'movable' contact, the 'coil 20 is shorted out lof the circuit. This produces variations in the current flowing through the prirnary winding of the transformer 22. The current flowing through Itheprimary winding ,of the transformer 22 passes directly between the left 'and intermediate terminals of the connector board 24 in FIG. 1 when the automobile battery is adapted to Vsupply 6 volts. For the cars employing 12-volt batteries', the current passes through the resistance 26 between the left and intermediate terminals of the connector board 24. VIny this way, the system constituting this invention is easily adapted for use with both types of automobile batteries Y included at present in automobiles.

VThe variations in the `current Flowing through the primary winding of the transformer 22 during alternate half cycles in thewoperationrot thevibrator 18 cause Ya Yvoltage 4to be induced in the secondary winding :of the transformer 122. The Voltage induced in fthe secondary winding has an increased amplitude relative ,Ito the voltage `induced inthe primary because of the turns ratios in the windings. Y'lhe increased voltage in the secondary winding of the transformer 22 is rectiiied by the stage formed by the capacitances 34 and 33 and the diode 316." 'I'he voltage is introduced through suitable resistanccs to the screen grid lof the tube 6:6 and the plate of the tube 60 and is also introduced through the coil 40' to the plate of the tube 46.

When a positive potential is introduced :to the plate of the tube 60, current flows through the tube and the tuning coil 64. The coil 64 and the capacitance 70 provide a tuning circuit resonant lat a relatively high frequency constituting .la rst modulating frequency. This frequency is seleotedon an individua-l basis for dilerent installations 'and is variable in accordance with adjustments made in the tuning coil d4.' As may be seen in the chart shown in FIG. 6, at least seven `diierent modulating frequencies of relatively high value may be provided by adjusting the tuning coil 6d. These frequencies may be selected in a range between 29` kilocycles per second and 52 kilocycles per second. It should be appreciated that both the range of the modulating signals at the high frequencies and the numberof choicesin this range may be considered as arbitrary and that a different range and a different number fof choices in the range may Y contacts of the switch 16, the lmovable and lower stationary contacts `of the vibrator 13, tand the righlt and intermediate terminals in the connector boand '74. This circuit is established only during the time that the right and intermediate terminals in the connector board 74 are bridged by a lead to produce the operation designated as high and low frequencies in FIG. 8. By grounding 9 the capacitances 72 and 76 in alternate half cycles, the capacitances 72 and 716 are placed in parallel with the capacitance 70 to vary the resonant frequency lof the tuning circuit formed by lthe capacitances and @the tuning coil 64. v

The introduction of the capacitances 72'and 76 to the tuned circuit Iformed by the coil 64 and the capacitance 70 causes the resonant frequency of the tuned circuit to decrease. The amount of the decrease in :the resonant frequency is ldependent upon the values of the capacitances 72 and 76 and can be varied by adjusting lthe value of the Vcapacitance 76. By proper adjustments in this value, the resonant frequency can be varied in increments between fa suitablerange such as 9l kilocyclcs per second' and 35.5 'kilocycles per second. For example, at least nineincrements in range such as shown in FIGS. 6- and 7 can be obtained by proper adjustments in the value of the capacitance 76. It should be appreciated that this range and the number of choices in the range can also be considered as arbitrary and, therefore, can beiamended without affecting the scope of the invention.

It will thus be seen that modul-ating signals of first and -second frequencies areproduced in the tube 69 on a timesharing basis. In alternate half cycles of the vibrator 1S, signals of relatively high modulating frequency yare produced, and in the other half cycles signals of a relatively low modulating frequency -are produced. A considerable number of different combinations of relatively high and low modulating frequenciesy can be obtained by ladjusting the tuning coil 64 and the capacitance 76.

As will be seen from the subsequent discussion, each installation at a garage is provided with fa `different comhination of low and high modulating frequencies to distinguish the installation from all other installations in the neighborhood. A Igarage door can be operated only when the receiver at the door receives carrier signals modulated with both low and high modulating frequencies of selected values. lIt should be appreciated that the ranges of the low and high modulating frequencies tend to overlap somewhat. However, combinations -should Ibe provided only where the high modulating frequency exceeds the low modulating frequency. This tends to restrict somewhat the number of combinations between the low and high modulating frequency, but a sufiicient number of combinations are still available to provide .a distinction between different installations in ya neighborhood.

A possible number of different combinations of low and high modulating frequencies may be seen from the chart shown in FIG. 7. As will be seen, the combinations not considered desirable are indicated by an X in the chart shown in FIG. 7.l Nineteen possible combinations are designated by an X out of a total of 63 such possibilities so as to leave 44 actual possibilities. The chart shown in FIG. 7 also indicates the value of the capacitance 72'which has to be `added in microfar-ads in order to obtain the selected frequency in the lo-w modulating range. As will be seen, the capacitance 72 would not have to be included `for -at least some `of the ac-tual combinations available.V It should be appreciated that the inclusion of the capacitance 72 only produces a rough approximation of the desired frequency `and that fine variations may have to be made by adjusting the capacitance 76 in order to obtain the desired frequency.

FIG. 8 illustrates the possible connections between the different terminals in the connector board 24. For the production of both low and high frequencies on a timesharing basis -as set forth above, the intermediate and right terminals are connected together. When modulating signals 'at only the low frequency are desired, the left and intermediate terminals are connected together. This causes -a ground to be constantly established to the capacitances 72 and 76 regardless of the positioning of the movable contact in the vibrator '18 such that the capacitances are always included in the tuned circuit.

For the production of modulating signals` at only the high frequencies, no connections are made between the different terminals in the connector board 24. This prevents the capacitances 72 and 76 from being grounded regardless of the positioning of the movable Contact of the vibrator 1S. Since the capacitances 72 and 76 'are never grounded, the tuned circuit is constantly formed only by the coil `64 and the capacitance 70 to provide modulating signals at the high frequencies. The connections to the terminal board 74 for obtaining either signals of low modulating frequency or signals of high modulating frequency are provi-ded for certain reasons. For example, an important reason is to facilitate the alignment of the receiver and the transmitter to the selected modulating frequencies so that the receiver will respond properly to the transmitted signals. By testing for each modulating frequency separately, problems resulting from the production of harmonic signals are considerably reduced. n

The modulating signals produced on the plate of the tube 60 yare introduced to the control grid of the tube 46 through the coupling capacitance S8 and the resistance 48. The tube 46 is included in a modified Colpitts type of oscillator. The oscillator also includes the crystal 44 and the resonant circuit formed by the coil 40 Iand the capacitance 42. This resonant circuit is tuned to substantially the same `frequency as the resonant frequency of the crystal 44. This frequency may have a suitable value such as .approximately 27 i12 megacycles. However, it will be appreciated that any other suitable carrier frequency can also be used. The frequency of the carrier signals produced by the modified Colpitts oscillator is designated for .all manufacturers by the Federal Communications Commission. Since all manufacturers Iare assigned the same carrier frequencies, it is important that a garage installation of one manufacturer should not be affected by signals from transmitters installed in automobiles by other manuy facturers.

The power output represented by the carrier signals from the tube 46 is limited in accor-dance with the requirements of the Federal Communications Commission. This power input is ydesignated as milliwatts maximum to the tube 46. The power limitation is obtained by limiting the potential on the screen grid of the tube 46 to that approaching ground. The potential on the screen grid of the tube 46 is controlled by the action of the network formed by the resistancesSS and 52. However, it should be appreciated that 4an increased potentialcan be applied to the screen grid of the tube 46y if no power limit-ations are imposed on the transmitter by Agovernmental :authorities.

'Ihe carrier signals produced by the modified Colpitts oscillator are modulated on a time-sharing basis with the :signals of vlow and high frequencies produced on the plate of the tube `60. These signals are induced from the coil 40 to the coil '11 so that they can be transmitted by the Vantenna 1f? to the antenna "10ft (FIG. 2) at the garage door. The signals received by the antenna 100 are introduced to the coil 102 and are induced by that coil in the coil 104. The signals are then introduced to the control grid of the tube `1'1-2 to obtain an amplification of the signals in the stage which includes that tube.

AThe sign-als yfrom the radio frequency (RF) stage 'are introduced through the tnansformer 122 to the detector stage which includes the diode 124. rThe detector stage operates to demodulate the signals by eliminating the carrier frequency. The -output signals from the diode 124 represent the modulating signals lat the low 'and high afrequencies on a time-sharing basis. These signals [are amplified -by lthe stage including the tube 132 yand fby the stages including the tubes 142 and 15G.

The amplified signals from the tube 15d are lintroduced to the tuned circuit formed 4by the coil 170 Iand the capacitance 172 :and to the tuned circuit formed by the coil 174 and the capacitance 176. The circuit formed by the coil and the capacitance 172 is tuned to the low modul-atingY frequency so as to pass signals only Kat that frequency. Similarly, the circuit formed by the coil 174' 'and the capacitance 176 is tuned to pass signals only at the fhigh modulating frequency. ln this Way, the tuned circuits act to channelize the modulating signals of selected low and high frequencies into dilerent channels.

' The signals passed by the tuned circuits have amplitudes within relatively narrow limits because of the limit. ing action provided by the diodes 160 land 156. For example, signals having ia positive lamplitude @above ground would pass through the diode 156 vto ground such that they would beunable to be presented to the tuned oir-V cuits. Similafrly, signals yhaving a negative amplitude greater than -2 volts would be absorbed by the action of the diode 168 so as to be prevented .from being introduced to the tuned circuits. The action of the diodes 156 Vand 160 in limiting the amplitudes of the signals introduced to the tuned circuit is important in obtaining the proper operation of Ysubsequent stages, as will become more apparent subsequently. Actually, the diodes 156 and 168 are biased-at a potential approximating -1 volt because of the iiow of leakage current through the diodes. The diodes than act to limit any signal swing to an amplitudeof l volt on either side of the bias of -l volt.

The modulating signals passed by the coil -170 and the capacitance 172.r 'are introduced through the coupling capacitance 180 to the control grid of the tube 184. These signals modulate the liow of current through 4a circuit including the power supply 123, the resistance 228, the coil 218,V the resistance 188 and the tube 184. The lresultant amplified alternating voltage produced on the 'plate of the tube 184 is fed back through the capacitance V192 to the Vcathode of the diode 196 for rectilication by vproduction o-f an lamplified direct voltage are accomplished in a single tube.vr This direct voltage causes a direct current to flow through the relay 218 and the resistance 220. The current flowing through the relay coil 218 has lan amplitude within relatively narrow limits because of the limiting action provided by the resistance '188. Y The tube 186 has a vcurrent 'iiow through it upon a passage of signals through the tuned circuit formed by the coil 174 and the capacitance 176. The resonant signals produced on the plate of the tube 186 are introduced through the capacitance 194 to the 'cathode of the diode 286 to obtain a rectification of the signals. These rectiied signals are then smoothed by the capacitance 214 so that a corresponding positive direct voltage is introduced to the control grid of the. tube 186. In this way, a direct current flows through the relay coil 218 and the tube 186 upon the introduction of an Ialternating signal to the control grid of the tube. This current has an amplitude Within relatively narrow limits because of the limiting action provided by the resistance 190.

The relay coil 218 is provided with parameters so that it can actuate the switch 224 only when current flows through both the tube 184 and the tube 186. In this Way, the rel-ay coil 218 can be operated only upon the reception at the receiver of modulating signals havingthe selected values at the low range and at the high range. The relay coil 218 can Ibe actuated only upon the receptionof modulating signals having the required low and high frequencies since euch modulating signal is incapable of producing the required .magnetic force in the relay coil 218. for actuating the switch 224. This results l2. #also results 'in part from the 'action of the resistances 188 Iand 190. Y

The llimiting action provided "by the diodes 156 and Y, 160 is instrumental in preventing Iany Iringing action in the tuned circuit formed by the coil and the-capacitance 172 or in the tuned circuit formed by the coil 174 land the capacitance 176. If ringing were to occur in the tuned circuits, it would prolong the time of response of the circuits. This would tend to produce an actuation ofV resistances 188 and 1901act` in this manner by limiting the 'Y llow of current through the relay 218 at any instant. By limiting the flow of current throughthe relay 218 at any instant, the relay is able to `become energized suiiciently only on la cumulative basis to actuate the switch 224.

The capacitance 222 is included to provide a time delay for insuring that the switch 224 will become actuated only upon the continuous transmission of signals at the desired modulating frequencies from the transmitter and not as a result of any random'varying generation of signals. The capacitance operates in this manner since it delays the build-np of any potential across the relay 218 for -a particular period of'tim'e such asiat least 1 second. Y

The apparatus disclosed above has certain importantV advantages. It is able to provide a discrimination between a multitude of different installations in a neigh-` borhood even though the receivers at the diierent installations may all receive carrier signals at the same frequency. This results from the use of diierent cornbinations of modul-ating signals at low and high frequencies. For example, 44 diivferent combinations of modulating patterns can be obtained when seven possible modulating frequencies are made available in the low` range and nine possible modulating frequencies are made available in the high range. This may be seen from the chart shown in rFIG. 7. Correspondingly increased numbers of combinations may be made available by increasing the number of choices in the low and high modulating ranges. By providing these different combinations, a clear-cut discrimination between differentV installations is obtained so that only the garage door at the desired installation becomes operated The apparatus constituting thisrinvcntion has certain' other important advantages. IFor example, the circuitry at the transmitter for producing the modulating signals at the low and high frequencies is relatively simple. This results from the production of the modulating signals at v the two frequencies on a time-sharing basis. By producing the signals on a time-sharing basis, the same tuned circuit can be `used to produce each frequency but addi-Y tional reactance is inserted into the circuit periodically to change from one of the modulating frequenciesrto the other.

Additional advantages are also obtained from theparticular construction of the transmitter. I'his results from the use of a single integral push button for obtaining the operation of the system constituting the invention. When depressed, this push button causes the radio receiver in an automobile to Vbecome shorted laga-inst the reception of any signals. At the same time, kor preferably slightly thereafter, the depression of the' switch causes power to be introduced to the stages Vfor producing the carrier signals and the modulating signals. This sequence of operations prevents the radio receiver'in the automobile from being damaged by any signals radiated by the antenna when 'signals are being transmitted toward the receiver at the garage door. 1t also prevents any reactance 13 from being introduced to the antenna and the coil 1 -1 from the input to the automobile radio so as to affect the operation of these members. lIt also prevents signals from being produced or from being radiated toward a garage door installation except during the time that the push button is positively actuated.

The circuitry at the transmitter is also advantageous to the operation of the receiver. This results from the fact that the signals at each of the two modulating frequencies are produced at the transmitter on `a time-sharing basis v and consequently are introduced to the receiver at separate times. This avoids the production of beat frequency signals and harmonics which would other-wise be produced if signals at the two modulating frequencies were introduced to the receiver at the same time.` Since the signals at the two modulating frequencies are introduced to the receiver on a time-sharing basis, they can be easily and simply separated by the use of two resonant circuits tuned to the proper frequencies.

The receiver is also advantageous for another important reason. It provides a very convenient circuit for converting the alternating signals passing through the tuned circuits into a proportionate direct voltage. This direct voltage is Vampliiied in the same circuit as that which receives the alternating voltage from the tuned circuits. The circuit is vso constructed that a relay in the circuit can become suliiciently energized to actuate a switch only when modulating signals at the selected frequenies are able to pass through both of the tuned circuits. By converting in one stage the alternating signals into a proportionate direct voltage and using the direct voltage to control lthe operation of a relay, increased accunac-ies and sensi-tivities in the operation of the' relay are obtained and without any increase in the number of required stages.

'The apparatus constituting this invention has certain other important advantages. This results from the packaging of the transmitter shown in lPIG. 1 and from the construction of the housing and the attachment of the housing to the dashboard of an automobile. As will be seen in FIG. 3, the transmitter is adapted to be attached to the dashboard 300 of an automobile at a position preferably under the dashboard and preferably directly beneath a radio 302 in the automobile.

The housing for the transmitter includes a first casing generally indicated at 304 in FIG. 4. The casing 304 is provided with a top wall 306, a pair of spaced side walls f 308 and a rear Iwa-ll 310. Pairs of holes 312 are provided in the top wall 306 at spaced positions in the longitudinal direction. The holes -312 in each pair are preferably disposed near the side walls 3018 to provide a iirm engagement between the casing 304 and the dashboard 300. This engagement is obtained by screws 314 which pass through any selected holes and into the dashboard 300;

A stud 318 extends downwardly from the top wall 306 of the casing 304 at a position intermediate the side walls 308 and toward the front of the casing. The stud 31'8 is internally threaded to receive a fiat-headed screw 32d extending upwardly through la hole (not shown) in a casing generally indicated at 3120. The casing 320 is provided 'with a bottom wall 322 and a

front wall

312,4

(1F-1G. 5) to form an enclosed housing .with the casing 304. The casing 320 is also reinforced by a -p-air of upwardly turned lateral flanges 325 (FIG. 4) which become disposed lwithin the side 'walls 3013 of the casing 304. The bottom Wall 322 of the casing 320` is adapted to Vrest on a flange portion 326 extending horizontally inwardly from the rear wall 310 of the casing 304.

A name plate 328 is easily attachable to the front Wall '324 of the casing 320 as by tabs (not shown). Since the name plate 3218 is the member primarily visible to the riders in the automobile, it can be provided with the name of the manufacturer and can be provided with a pleasing appearance. A push button 330 (IFIGS. 4 and Y ld- 5) extends through holes in the front wall3$4 and in the name plate 328. The push button 330 is coupled to the switches `14 and 'le in FIG. l to obtain a closure of the switches l:upon a depression of the push button and is spring-loaded as at 332 to maintain the switches in the normally opened position.

The casing 304 is initially attached to the dashboard 300 as by the screws 314. The casing 320 is thereafter attached to the casing 304 as by the nat-headed screw 321. Since the casing 320 carries all of the electrical components forming the transmitter shown in FIG. l, the transmitter can be easily removed from the dashboard 300 for any desired adjustment or repair merely by removing the Screw 321. A cable (not shown) leading to the (radio (not shown) is included in the transmitter and is supported by the casing 320. The cable extends to the radio through an opening 334 in the rear wall 310 of the leasing 304. Another cable also extends through the opening 334 to the antenna 10.

The apparatus described above is primarily adapted for use to provide a remote control over the operation of a garage door. It should be appreciated, however, that the apparatus constituting this invention is also adapted for other uses. For example, the transmitter can be disposed within a house and the receiver can be disposed in an automobile to obtain an automatic starting of the automobile a few minutes before the driver is ready to leave the house. vIn this way, the automobile engine can become fully warmed on winter days at the time that the driver is ready to leave.

The apparatus constituting this invention has been described primarily in connection with the production of modulating signals having low and high modulating frequencies. It should be appreciated that the modulations can be obtained in other ways than by differences in frequencies. For example, modulating signals having rst and second characteristics can be produced by shifting the signals in phase to provide the signals with iirst and second distinctive phases.

It should be appreciated that semiconductors such as transistors can be used in place of the vacuum tubes shown in FIGS. 1 and 2 and described above. The reason for this is that both semiconductors and vacuum tubes serve as Icurrent control members.

Although this invention has been disclosed and illustrated with reference to particular applications, the principles involved are susceptible of numerous other applications which will be apparent to persons skilled in the art. The invention is, therefore, to be limited only 4as indicated by the scope of the appended claims.

1. In combination for controlling the operation of a garage door from a removed position in an automobile: an antenna connected in the automobile normally to receive radio signals for the reception of audio programs in the automobile; first switching means coupled to the antenna and operative to short circuit the input to the radio; second switching means coupled to the rst switching means for actuation with the first switching means; means coupled to the second switching means and operat-ive upon the actuation of the switching means to produce carrier signals at a lirst particular frequency and including means'coupled to the antenna for obtaining a transmission of the signals by the antenna; means coupled to the second switching means and operative upon the actuation of the switching means to produce modulating signals at a second particular frequency for modulating the carrier signals; means at the garage door for receiving the carrier signals; means coupled to the receiving means for demodulating the received signals to obtain only the modulating signals; and means coupled to the demodulating means for obtaining an operation of the garage door mechanism only upon the occurrence of modulating signals of the second particular frequency.`

arcaeri 2. In combination for controlling the operation of a garage door `from a removed position intantautomoble: an antenna connected inthe -automobile normally to receive radio signals for the reception of audio programs in the automobile; means including a first tuned circuit for producing carriersignalsV and including a coil magnetically coupled to the antenna for introducing signals to the antenna for transmission to the garage door; means including a second tuned circuit for producing modulat- Ying signalsv at a particular frequency and coupled to the responsive to modulating signals at the particular fre-Y quency for obtaining an operation of the garage door.

3. In combination for controlling theoperation of a garage door from a removed position in an automobile: an antenna connectedin the automobile normallyfto receive radio signals for .the reception of aud-io programs in the automobile; means including a first tuned 'circuit for producing carrier signals and including a coil magnetically coupled'to the antenna for introducing signals to the antenna for transmission to the garage door', a second tuned circuit resonant at a first particular modulating frequency and coupled to the first tuned circuit for providing a modulation of the carrier signals; means including reactance means disposed electrically for kcoupling to the tuned circuit and adjustable to produce a resonance in the circuit at a second particular modulating frequency; means including a first switclh operative upon actuation to short circuit the input to the radio; means including a second switch ganged to the first switch and operative upon actuation to introduce a potential to the first and second tuned circuits for obtaining the production of carried'and modulating signals; means coupled to the second switch and operativey upon actuation of the circuit to obtain resonance of the ,tuned circuit at a Y second modulating frequency; an antenna for receiving signals; switching means coupled to the antenna for inhibiting the reception of signals by theantenna upon the operation of the switching means; means operatively coupled to the reactance meansand the tunedY circuitV and to the switching means for establishing the connections between the reactance means and the tuned circuit and for disestablishing such connectionsl on a time-sharing basis upon the operation ofthe switching means to produce modulating signals alternately at the rst frequency and at the second frequency; means operatively coupled to the antenna and the last mentioned means for providing carrier signals ata third selected frequency and second switch to alternately obtain a coupling of the re- Y ternately obtain the production of signals at the first and second modulating frequencies; means at the garage for modulating the carrier signals with the signals alter- Vnately produced at the first and second frequencies to produce signals for transmission to the distant mechanism and for introducing 'such .modula'tedvsignals to the antenna for transmission by the antenna to the removedV position; means at the distant mechanism for receiving the transmitted signals; means coupled to the receiving means for separately demodulating the received signals .Y

to introduce modulating signals only at the first frequency to a tirst channel and to introduce modulating signals only at the second frequency to a second channel; and

means coupled to the demodulating means and responsive only to the modulating signals of both the first andV second frequencies on the time-sharing basis for produc'- ing an output signal for operating the distant mechanism. 6. In combination for controlling the operation of a distant mechanism from a removed position by obtaining the transmission of signals from an antenna normally adapted to rece-ive radio signals; first switching means cluding tuned electrical circuitry and including secondV switching means responsive to the actuation of the first switching means for alternately varying the characteristics of the tuned electrical circuitry to modulate the carrier signals with signals of a first selected frequency at first particular periods of time and for modulating the carrier signals with signals of a second selected frequency door for receiving the transmitted signals; means operai tive upon the-received signals for detecting the received signals to pass only the modulating signals; means coup'led to the detecting means and including-a first circuit resonant to pass modulating signals only of the first particular frequency and including a second circuit resonant to pass modulating signals only ofthe second particular frequency; and means responsive only to modulating signals of both the first and second particular frequencies to obtain operation of the garage door.

4. The combination set forth in claim 3, in which the door-operating means includes a pair of stages each coupled to a different one of the resonant circuits to receive modulating signals of a different one of the two selected frequencies and each constructed to amplify 'the modulating signals and including unidirectional means to convert the amplified alternating signals into a proportionate direct current and in which the door-operating means includes means coupled to the last-mentioned stagesffor operation only upon the concurrent fiow of a direct current through both of the stages.

5. In combination for controlling the operation of a distant mechanism from a removed position: a tuned different from the first frequency at second particular periods -alternating with the first particular periods; means responsive to the lmodulated carrier signals for transmitting the modulated carrier signals toward the distant mechanism; means at the distant mechanism for receiving the transmitted signals; detecting means operative upon thereceived signals to pass only the modulating signals; means including tuned electrical Ycircuitry responsive to the modulating signals for separately passing the first modulatingy signals of the first selected frequency and theV second modulating signals of the second -selected frequency; means including rst detecting means responsive to the first modulating signals to produce a first detected signal and including second detecting means responsive to the second modulating signals to produce a second detected signal and including means coupled to the first and second detecting means for producing an output signal only upon the sequential production of the first and second detected signals; and means responsive to the output signalsfor obtaining an operation of the distant mechanism.

7. In combination for controlling the operation of a distant mechanism from a removed position by obtaining the transmission of signals to the removedV position by an antenna normally adapted' to receive radio signals:` a capacitance; means including a first tuned circuit and first switching means for alternately coupling the capacitance into the circuit and isolating the capacitance from'the circuit upon alternate operations of the firstswitching means to produce modulating signals having first and second particular `frequencies on a particular time-sharing basis; means including a second tuned circuit for providing carrier signals and coupled to the first tuned circuit and tothe antenna for modulation of 4the carrie-r signals ;by the modulating signals having the first and second particular frequencies and for transmission of the modulated carrie-r signals-by the antenna tothe distant mechanism; second switching means operatively coupled to the antenna-for preventing the reception of signals by the antenna upon the actuation ofthe second switching means and operatively coupled to the first switching means for obtaining the alternate operation -of :therst switching means upon the actuation of the second switching means; receiving means at the distant mechanism; detecting means 4coupled to the receiving means for extracting the modulating signals; first means coupled tothe detecting means and resonant at the first modulating frequency for p-assing onlyA the -first modulating signals; second means coupled to the detecting means land resonant at the second modulating frequency for passing -only Athe second modulating signals; first detecting means coupled to the first resonant means for converting the first modulating signals into a first direct voltage related to the amplitude of the signals; second detecting means coupled to the second resonant means for converting the second modulating signals into a second direct voltage related to the amplitude of the signals; vmeans coupled to the lfirst and second detecting means and responsive only to the cumulative effect of the first and second direct voltages for producing an output signal; and Vmeans responsive to the output signal for obtaining an operation of the distant mechanism.

8. In combination for controlling the operation of a distant mechanismfrorn a removed position by obtaining the transmission of signals to theremoved position by an antenna normally adapted to receive radio signals: a tuned circuit resonant at avfirst particular frequency; switching means operatively coupled tothe antenna forpreventing the reception of signals rby the antenna upon the actu-ation of the switching means; resonant means including a capacitance disposed electrically for coupling to the tuned circuit and adjustable to produce a resonance in the circuit at a second particular frequency; second switching means operative at a particular repetition rate and responsive to the actuation of the first switching means to connect the capacitance into the tuned circuit and to disconnectthe capacitance from the circuit on a time-sharing basis related to the particular repetition rate; -means for providing carrier signals at a third particular frequency andV operatively coupled to the :resonant means for obtaining a modulation of the carrier signals with the signals at the first and second frequencies |and operatively coupled to the antenna for obtaining a transmission of the modulated carrier signals by the antenna to the distant mechanisrn upon the actuation of the switching means; means at the distant mechanism for receiving the transmitted signals; means coupled to the receiving means `for demodulating the received signals to produce modulating signals alternately at the first frequency and at the second frequency; and means coupled to the demodulating means for producing an operation of the distant mechanism only upon the alternate passage of modulating signals at the first and second :frequencies through the demodulating means at the particular repetition rate.

9. In combination for controlling the operation of a garage door from a removed position in an automobile and for simultaneously preventing theV reception of, radio signals by an antenna on the automobile: means operatively coupled to the antenna for providing carrier signals at a selected frequency and for introducing the carrier signals to the'fantenna for transmission by the Vantenna toward the garage door; switching means operatively coupled to the antenna for preventing the reception of signals by the antenna upon the actuation of the switch- M18 ing means; means operative upon the carrier signals and responsive to the actuation of the switching means for modulating the vcarrier signalswith 4alternating signals of a particular frequency; means at the garage door for receiving the modulated carrier signals; means responsive to the modulated carrier signals :for detecting the modulated carrier signals to pass onlythe modulating signals; a

stage responsive to the modulating signals from the detecting means and including a current control member for amplifying the signals and including unidirectional means for rectifying the signals from the current control memfber and-including a capacitance for smoothing the rectified voltage into a direct voltage and including impedance meansfor feeding the direct voltage to the current control member forfurther amplification by the current control member of the direct voltage; and means including a relay responsive to the flow of Idirect current through the cur- -rent control mem-ber to obtain the operation of the garage door.

l0. In combination for controlling Athe operation of a 4garage door from a removed position in an automobile and for simultaneously preventing the reception of signals 4by an antenna on the automobile: switching means operatively coupledto the antenna for preventing the reception of signals -by lthe antenna upon the actuation of the switch- 4ing means; means including electrical circuitry responsive to the `actuation of the switching means for providing .modulating signals of a selected low frequency and modulating signals of a selected high frequency on a timesharing basis; means including electr-ical circuitry opera- 'tivelycoupled to the antenna and the last mentioned means forV providing carrier signals of a third selected frequency Jandfor modulating the carrier signals with the modulating signals of the selected low and high modulating frequencies and for introducing -the modulated signals to the antenna -for transmission by the antenna toward the garage door; means including electrical circuitry at the garage door for receiving the transmitted signals; means including electrical circuitry coupled to the receiving lmeans yfor detecting the received signals; means including first resonant circuitry responsive to the modulating signals of the selected low frequency and including second l resonant circuitry responsive to the modulating signals of the selected high frequency for separately passing the signals of the selected frequencies; a first electrical stage responsive to the modulating signals of the selected high modulating frequency from the resonant means and including first current control means for amplifying the signals and including first undirectional means for rectifying the amplified signals from the current control means and including a first capacitance for smoothing the rectified voltage from theunidirectional means into a direct voltage and including first impedance means for introducing the `direct voltage from the first capacitance to the current control mea-ns for amplification of the direct voltage; a second electrical stage responsive to -the modulating signals of the selected low modulating frequency from the resonant means and including second current control means for amplifying the s-ignals and including second unidirectional means for rectifying the amplified signals from the second current control means and including a second capacitance for smoothing the rectified voltage from the unidirectional voltage into a direct voltage and including second impedance means Afor introducing the direct voltage lfrom the second capacitance to the current control means for amplification of the direct voltage; means including a relay responsive to the current through Ithe first and second current control means to become energized only upon a concurrent flow of current through these means; and means responsive -to the relay when energized to obtain an operation of `the garage door. Y

l1. In combination for controlling -the operation of a Igarage door from a removed position in an automobile and for preventing the reception of signals -by an antenna on the automobile: switching means operatively coupled the antenna upon an actuation of the switching means; means including a tuned coil and a rst capacitance connected across the coil for providing modulating signals haying a selected high frequency; means including a second capacitance electrically connected to become coupled to the tuned coil and the first capacitance for providing modulating signals having a selected low frequency; means including a vibrator operatively coupled to the switching means for producing an alternate vcoupling of. the second capacitance to the first capacitance and the tuned coil and an alternate de-coupling of the second capacitance from the tuned coil and the first capacitance upon an actuation ofthe switching means; means including a tuned circuit for producing carrier signals and for modulating the signals with the modulating signals of low and high frequencies and for introducing the modulated signals to 'the antenna for transmission by the antenna toward the gara-ge door; means at the garage door for receiving the transmittedrsignals; means coupled to the receiving means for detecting the received signals to pass only the modulating signals; means responsive to the signals from the deringing in the resonant means; and means coupled to the first and second resonant means and responsive only upon the concurrent introduction of the modulating signals of the selectedlow and high frequencies to provide anoperation of the garage door.

12. The combination set forth` in claim 11, in which: the door-operating means includes a first stage for receiv- Ving the modulatingsignals of limited amplitude and of the selected low frequency and in which the first stage includes a first current control member for amplifying these signals and in which the first stage includesfirst means for rectifying and smoothing lthe amplified modulating signals from Vthe first current control member into a `direct vol-tage and in which the first stage also includes first means for introducing vthe direct volta-geffro'm the rst rectifying and smoothing means to the first current control member and in which the first stage includesV first means for limiting the current through the first current control member; and in Which'the door-operating` means includes a second stage for receiving the modulating signals of ylimited amplitude and of the selected high frequency and in which the second stage includes a second current control member for'arnplifying these signals and in which t'ne second stage includes second means for rectifying and smoothing the amplified modulating signals` from the second current control member into a directV Voltage and in which the second stage also includes second means :for introducting the direct voltage from -the second rectifying and smoothing means to the second current control 'member and in which the second stage includes sec References Cited in the file of this patent UNITED STATES PATENTS y 1,654,927 Farrington Ian. 3, 1928V 2,500,212 Starr Mar. 14, 1950 2,522,893 Purington Sept. 19, 1950 2,565,540 Williams Aug. 28, 1951 p 2,662,109 Tapp et al. Dec. 8, 1953 2,675,544 Trimble Apr. 13, 1954 2,699,301 Clute Jan. 11, 1955 2,705,321 Beck et al Man/29, 1955 2,724,074 Welker Nov. 15, 1955 2,788,521 Undy Apr. 9, 1957 2,841,700 Handen July 1 195s 2,847,497 Appleton et al. Aug. 12, 1958 2,931,956 van Andale Apr. 5, 1960 FOREIGN PATENTS 125,838 Australia Oct. 21, 1947

Claims

1. IN COMBINATION FOR CONTROLLING THE OPERATION OF A GARAGE DOOR FROM A REMOVED POSITION IN AN AUTOMOBILE: AN ANTENNA CONNECTED IN THE AUTOMOBILE NORMALLY TO RECEIVE RADIO SIGNALS FOR THE RECEPTION OF AUDIO PROGRAMS IN THE AUTOMOBILE; FIRST SWITCHING MEANS COUPLED TO THE ANTENNA AND OPERATIVE TO SHORT CIRCUIT THE INPUT TO THE RADIO; SECOND SWITCHING MEANS COUPLED TO THE FIRST SWITCHING MEANS FOR ACTUATION WITH THE FIRST SWITCHING MEANS; MEANS COUPLED TO THE SECOND SWITCHING MEANS AND OPERATIVE UPON THE ACTUATION OF THE SWITCHING MEANS TO PRODUCE CARRIER SIGNALS AT A FIRST PARTICULAR FREQUENCY AND INCLUDING MEANS COUPLED TO THE ANTENNA FOR OBTAINING A TRANSMISSION OF THE SIGNALS BY THE ANTENNA; MEANS COUPLED TO THE SECOND SWITCHING MEANS AND OPERATIVE UPON THE ACTUA-