US2300081A - Method and apparatus for radio receiving - Google Patents

Method and apparatus for radio receiving Download PDF

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Publication number
US2300081A
US2300081A US321379A US32137940A US2300081A US 2300081 A US2300081 A US 2300081A US 321379 A US321379 A US 321379A US 32137940 A US32137940 A US 32137940A US 2300081 A US2300081 A US 2300081A
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receiver
carrier
frequency
voltage
tube
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US321379A
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Sidney Y White
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Priority to NL65298D priority patent/NL65298C/xx
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Priority claimed from US321378A external-priority patent/US2283523A/en
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03J—TUNING RESONANT CIRCUITS; SELECTING RESONANT CIRCUITS
    • H03J7/00—Automatic frequency control; Automatic scanning over a band of frequencies
    • H03J7/18—Automatic scanning over a band of frequencies
    • H03J7/20—Automatic scanning over a band of frequencies where the scanning is accomplished by varying the electrical characteristics of a non-mechanically adjustable element
    • H03J7/22—Automatic scanning over a band of frequencies where the scanning is accomplished by varying the electrical characteristics of a non-mechanically adjustable element in which an automatic frequency control circuit is brought into action after the scanning action has been stopped
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03J—TUNING RESONANT CIRCUITS; SELECTING RESONANT CIRCUITS
    • H03J7/00—Automatic frequency control; Automatic scanning over a band of frequencies
    • H03J7/02—Automatic frequency control
    • H03J7/04—Automatic frequency control where the frequency control is accomplished by varying the electrical characteristics of a non-mechanically adjustable element or where the nature of the frequency controlling element is not significant
    • H03J7/042—Automatic frequency control where the frequency control is accomplished by varying the electrical characteristics of a non-mechanically adjustable element or where the nature of the frequency controlling element is not significant with reactance tube
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03J—TUNING RESONANT CIRCUITS; SELECTING RESONANT CIRCUITS
    • H03J7/00—Automatic frequency control; Automatic scanning over a band of frequencies
    • H03J7/18—Automatic scanning over a band of frequencies
    • H03J7/20—Automatic scanning over a band of frequencies where the scanning is accomplished by varying the electrical characteristics of a non-mechanically adjustable element

Definitions

  • This invention relates to a radio receiver adapted to receive signal communication from a plurality of transmitting stations, and in which means is provided which is actuated by impulses sent from the transmitting station, for the purpose of identifying the particular station which is transmitting and for permitting the transmitting station to communicate with a desired group of receivers or with an individual receiver of the group.
  • This invention is in the nature of an improvement on the invention disclosed and claimed in application Serial No. 321,378 led February 29, 1940, in my name.
  • a radio receiver which is especially adapted for the reception of carrier waves having a frequency higher than 20 megacycles, and wherein inertialess scanning means are provided for rapidly scanning a portion of the spectrum in which a tone modulated carrier is expected to occur and for causing the receiver to automatically lock on such a carrier. It is desirable in connection with such a receiver to provide an indicating device, such as an alarm, which will notify the operator that a carrier has been locked on and the calling party is ready to speak to him. It is an object of this invention to provide an alarm device which will give an audible signal to the operator when the receiver has locked on a carrier.
  • the alarm device is also operative to indicate the reception of a carrier by a scanning receiver which is provided with a director device for causing it to lock on the rst carrier encountered, such a receiver being disclosed in patent application Serial No. 321,377, referred February 29, 1940, in my name.
  • a call may be transmitted from station A directed to station B.
  • B is to set up a communication channel with A, he must obviously know who is calling so that he may arrange for the transmission of a tone frequency which As receiver will lock on.
  • this indicating device comprises a series of electric lights on which are painted or otherwise marked the station designation, such as A, B, C, D, etc., and which are lighted in accordance with the station on which the receiver is locked. 'Upon B nding that A is calling, he may then set up a transmission modulated by the identifying tone upon which As receiver only will lock and the indicating light marked B on As receiver Will light, indicating that the circuit is complete and that he can commence talking It is only after Bs receiver has locked on As carrier that energy impulses may be transmitted by station A to operate the indicator of Bs receiver.
  • the station designation such as A, B, C, D, etc.
  • Diierent forms of station identifying impulses might be used to operate the indicator as, for example, a selective audio tone in addition to the already existing tone which causes the locking action. It is a further object of the invention to operate the indicator by means of energy pulses in the form of a series of dots. The number of dots will determine the identiiication of the transmitting station, for example, station A would transmit one dot, station B two dots, station C three dots, etc.
  • a still further object of the invention is to provide a radio receiver with means whereby communication may be selectively established With all the receivers in a group, with a limited number of such receivers or with only an individual receiver of the group. Considering, for example, a group of 100 receivers, all could be made to lock on the general call tone frequency of, for example, 5000 cycles, and by means of a step-by-step relay having a contact arm movable over a plurality of contact points, the contact arm may be moved to contact number l by transmitting one dot.
  • each receiver is preferably also provided with means which cause it to lock on a carrier modulated by another tone frequency.
  • a sub-group of 10 receivers of the entire group of 100 could be made to lock on a tone frequency of 7000 cycles, and by connecting the headphones of the receivers to different contact points, communication could be had with any desired receiver of the group of l0.
  • contact could be established with receiver A by sending two dots, with receiver B by sending three dots, etc. While a total group of 100 receivers has been referred to, it Will be understood that the invention is adapted for use with a considerably greater number of sub-groups of receivers, and practically an unlimited number of receivers in each sub-group.
  • Fig. 1 is a schematic circuit diagram in block form of the receiver portion of a radio receiving system embodying the invention
  • Figs. 2 and 3 are schematic circuit diagrams of a radio receiving system embodying the invention.
  • Fig. 4 is a schematic circuit diagram of a radio receiver adapted for use with the invention.
  • the receiver shown comprises an antenna I connected to the tunable input circuit 2 of a radio frequency amplifier 3, the circuit 2 being permeability tuned over a band of frequencies as indicated at 4.
  • ferromagnetic .cores known under the trade name Aladdinite are very satisfactory. These cores are made from a synthetically produced ferromagnetic mass powder consisting substantially Wholly of magnetic oxide of iron in the form of minute particles, substantially all of which, as they appear under a microscope, are of generally rounded form. These particles are preferably molded into cores by mixing with several per cent of Bakelite as a binder.
  • the output circuit of amplifier 3 feeds in turn a first detector or mixing device 5, an intermediate frequency amplifier 6, a second detector 1, audio frequency amplier V8, band pass filter 9, and a signal reproducing device I0, herein illustrated as ear phones, but it will be understood that this device is of a suitable type to reproduce any desired type of signal. If desired, the output level of the receiver may be maintained at a substantially constant Volume level by an automatic volume control device II which may be of any known type.
  • the amplier 3, mixing device 5, intermediate, frequency amplifier it, detector “I, and audio amplifier 8 maybe of any known type as used in superheterodyne receivers for the reception of modulated carrier waves.
  • the oscillator frequency is supplied to the mixing device by an oscillator I2, whose frequency is controlled by a control tube I3 which is subject to the control of a sweep oscillator I4 preferably generating a low frequency, such as a half cycle per second.
  • the control tube I3 is also subject to the control of a director device I5 which is in turn controlled by a switch device I6 operated by one of the tone filters I'I, I'I which are connectedy in parallel with the audio frequency amplifier 8.
  • the detailed construction of the amplifier 8, oscillators I2 and I4, control tube I3, director I5, switch I5, and tone filters II, I'I will be referred to later herein.
  • the frequency of the oscillator I2 is automatically controlled over a range of frequencies by the control tube I3 through the action of the sweep oscillator I4.
  • the switch l5 Upon encountering a tone modulated carrier which forms a beat frequency with that of oscillator I2 which lies within the acceptance band of the intermediate frequency amplifier 6, and to which the tone filter, for example the filter II, is responsive, the switch l5 is operated which causes the director device I5 to overcome th action of the sweep oscillator I4 and maintain the frequency of the oscillator I2 at a constantJ value, thus locking the receiver on the carrier.
  • the receiver will naturally remain locked on this carrier until the modulating frequency to which the tone filter I1 is responsive disappears or until the carrier disappears, in which event the sweep oscillator I4 again takes control of the oscillator I2 and the scanning action of the receiver is resumed.
  • the tone lter I'I of all the receivers may be made resonant to a common frequency, as for example 5000 cycles, so that upon the transmission of a carrier frequency modulated with this frequency, all the receivers of a group will lock on this carrier frequency, whereupon the operator at the transmitting station may communicate with every receiver in the group.
  • the tone filter I'l' is made resonant to a frequency which is individual to only one receiver of the group, so that the operator at the transmitting station rby modulating his carrier with this particular tone frequency may establish contact with that particular receiver of the group.
  • the heretofore described receiver of Figure 1 is indicated by the reference character R, the output of the receiver being connected by a transformer I8 to a tone filter I9, which is in turn connected to the coil 20 of a relay 2I, through a rectifier 22, a suitable resistor 23 being shuntecl across the terminals of the relay winding.
  • the armature 24, upon the operation of relay 2I, serves to close a circuit through the battery 25 and the coil of a step-by-step relay 26 having an armature 2l, pivoted, as at 28, and retained in its normal position against a stop T by a spring S.
  • the armature 21 carries a pawl 29 adapted to rotate a ratchet wheel 3i), the pawl being normally held in engagement with the ratchet 3B by means of a spring 3
  • a friction wheel 32 mounted on a spring 33 may be provided to engage the teeth of the ratchet 30 to prevent over-running thereof.
  • Ratchet 30 is secured to a shaft 34, to one end of which is secured a movable contact arm 35 adapted to selectively engage a series of contacts 36, 3l, 33, 39, 40.
  • a spiral spring 4I is provided, one end of which is connected to shaft 34 and having its other end fixed.
  • the contacts 3l, 39 and 40 are connected by means of the circuit shown to the laments of electric lights on whose globes may be painted or otherwise inscribed the designations of transmitting stations, herein indicated as A, C and D. Since the receiver herein illustrated is that of station B, no indicating light for this station is, of course, necessary.
  • a battery 42 is connected to the contact arm 35 to supply current for energizing the filaments of the lights and also to supply current to contact 36 for a purpose to be later described.
  • a circuit 43 which includes the plate and cathode of an electron discharge tube 44, a battery 45, and an electromagnet 4B, the control grid of tube 44 being connected to the automatic volume control circuit of receiver R. by the lead 41.
  • Circuit 43 also includes the coil of the relay 48 whose armature 49 is adapted to open and close a circuit connecting the contact 36 and an alarm device herein illustrated as a bell 50.
  • the contact arm 35 When the receiver is not locked on any carrier, the contact arm 35 is in engagement with contact 35 and the lbell 50 is unenergized.
  • the carrier Shortly after the receiver is locked on a tone modulated carrier by the means heretofore described, the carrier is modulated at the transmitting station with -an audio tone, as for example 800 cycles for a short period, such as one-quarter of a second, to form a dot impulse.
  • This impulse is transferred to the relay 20 through the ltransformer I8 and the tone lter
  • Vserves VtoV close the'circuit through battery 25 and the coil of relay 26, causing the armature 21 of the latter to advance the pawl 29 a distance of one ratchet tooth.
  • This causes the contact arm 35 to engage contact 31 and light the filament of lamp A which thereby provides a visual indication that station A is calling receiver B, the single dot being the identifying impulse associated with station A While contact arm 35 was still in engagement with contact 3B, and as soon as the carrier frequency of station A was received, a negative voltage is supplied to the grid of tube 44 by the automatic volume control action causing the tube 44 to become blocked and the release of armature 49 of relay 48, thereby closing the circuit including a battery 42, contact arm 35, armature 49, and bell 50, causing the bell 59 to give an audible indication that some station is calling receiver B.
  • the operation of the bell 59 continues for a short time until contact arm 35 is moved away from contact 36 by means of the dot impulse received.
  • three dot impulses are transmitted which cause the lpawl 29 to advance the ratchet wheel 30 three teeth and the contact arm 35 into engagement with contact 39 so that the circuit through the filament of light C is closed and the light indicates that station C is calling.
  • current passes through circuit 43 and the coil of the electromagnet 46 which withdraws the pawl 29 from the ratchet 30, whereupon the spring 4
  • the method of operation of the indicating device of Fig. 2 is similar to that above described.
  • a negativ-e voltage is built up by the AVC device of the receiver which is applied to the grid of tube 44 causing this tube to lbecome blocked.
  • This causes the relay 48 to release its armature 49, thereby causing the bell 50 to operate and give an audible indication that some station is calling.
  • the operation of the bell 50 continues until the contact arm 35 is moved away ⁇ from contact 35 by means of a received dot impulse in the manner above described.
  • Fig. 3 The embodiment of the invention shown in Fig. 3 is in general similar to that shown in Fig. 2, corresponding parts in the two gures being indicated by similar reference characters.
  • the relay 48 and bell 50 are omitted and the audio output of the receiver is impressed on contact arm 35 by the lead 5
  • a circuit 52 is shown connected to contacts 31 ⁇ and 39 and to ground and which includes the signal reproducing device, herein illustrated as a telephone receiver 53.
  • a carrier frequency modulated by the 5000 cycle tone frequency is transmitted.
  • all the receivers will have automatically locked on the transmitted carrier and the sending station then transmits one dot impulse, by also transmitting the 800 cycle modulation for a brief interval.
  • This dot impulse causes the operation of relay 2
  • the operators of all receivers may then listen in on the phones 53 to the communication from station A, thus permitting the operator of station A to issue a general order to all the station operators.
  • station A Should the operator of station A wish to set up a communication channel with station B only, he transmits a carrier frequency modulated with the '7000 cycle tone frequency to which the subgroup of receivers including receiver B is responsive. After a short interval, during which the receivers of this sub-group have locked on his carrier frequency, station A transmits 3 dots on the 800 cycle modulated carrier. The impulses thus transmitted cause pawl 29 to advance ratchet wheel 39 three teeth and contact arm 35 to engage Contact 39 thereby completing the circuit through lead 5
  • the circuit 52 of receiver A is connected to its contacts 31 and 38, and that this circuit of receiver C is connected to its contacts 31 and 40.
  • the circuit 43 of electromagnet 46 At the termination of the communication, upon the carrier wave of the transmitting station being no longer transmitted, current passes through circuit 43 and the coil of electromagnet 46, which withdraws the pawl 29 from ratchet wheel 30, whereupon the spring 4
  • a series of only 5 contacts is shown associated with contact arm 35, it will be understood that any desired number of contacts-may be provided in accordance with the number of receiversin each sub-group.
  • Fig. 4 in which the audio amplifier 8 is shown as comprising the tubes VTI and VTS which are resistance coupled, as shown, the latter tube also being provided with an lextra plate 54 which cooperates With the tube cathode 55 to provide a diode rectifier.
  • the output circuit of vtube'VTl is connected to the earphones I5 by means'of a band pass lter 9.
  • the filter comprises a push pull output transformer 56 which is designed to have a considerable amount of leakage reactance and whose primary winding has a condenser 51 connected across it.
  • a sharp lcut off above 3000 cycles is obtained so that any tone frequency of 4000 cyclescr higher ceases to be annoying to the user, even when the tone frequency is left continually on during the speech transmission. It is found that a lter of this type will allow the usual range of telephonie speech frequencies to pass and providea rapid attenuation above those limits.
  • the scanning device I4 comprises the vacuum tubes VT5 and VTS, the plate of each tube being connected to the grid of the opposite tube through the condenser CI and C2 having ya capacity of 0.5 mfd., and the grids of the tubes being connected to their cathodes through the 2.0 megohm resistors R5 and R6, to thereby produce a half cycle sweep voltage of substantially square wave form.
  • This voltage is supplied to the control grid of a control tube VT4v through a lead 58, resistor R'I and condenser C3, the latter serving to block off the direct current voltage.
  • Resistor R'I and condenser C4 act as a filter to l take voltage of square wave form at the plate of tube VT5 and change it to a substantially sinusoidal Wave form.
  • the resistor R1 being 10 megohms, reduces the voltage from several hundred volts to i3 volts.
  • vantage in making R'I so large is that it does not destroy the symmetry of the sweep oscillator I4. It will be realized that the half cycle oscillator covers the entire scanning spectrum in one direction completely in one second.
  • a con- Vtrol voltage is also supplied to the control grid of VT4 through resistor R5 and the director line 58 by the director device I5.
  • the director I5 consists of a director driver tube VTI whose control grid is connected through lead 59 and condenser 65 to the output of the intermediate frequency amplifier 6, the cathode of the tube being connected to ground through the resistors RI4 and RI5 connected in series.
  • the tube cathode is connected to the B supply voltage source through the resistor RI3 and the B supply is also connected through the resistor RIB to the screen grid 6I of the tube VTI and also to the plate of the switching tube VTIU, as shown.
  • the plate circuit of tube VTI comprises the low impedance primary windings 52 and 63 which are coupled, respectively, to the secondary transformer windings of the circuits TCI, TC, one of which is tuned to a frequency of from 5 to 10 kilocycles above the intermediate frequency,
  • Theoscillator I2 is shown as comprising the tube VT3 whose cathode is grounded and whose plate circuit is provided with a tuned tank circuit comprising the coil LI and condenser 64. Itis found that by making the condenser 64 of fixed value and varying the inductance of coil yLI so as to change its permeability, as by means of a powdered ferro-magnetic core, as indicated at 55, substantially equal percentage tuning effects are secured throughout the band of frequencies. struction to the core 4 above described.
  • the oscillator gridvv receives charging current through L2 representing the mutual inductance of the tickler coil with LI.
  • the grid current at the end of L2 is thus exactly out of phase with the circulating current in Ll.
  • the current Before reaching the grid Aof tube VT3, the current must pass through some series leakage inductance, represented by L3, which produces a reactance of rather small amount, but which is quite effective due to the very heavy current iiowing through it.
  • energy is supplied which is so phased in relation to that of the plate tank circuit as to cause the tube to oscillate, but is not quite 180 phase angle from the plate.
  • the amount of phasing may be varied as desired, by making L3 of the proper value, even, if necessary, by winding an additional uncoupled coil in series with the grid, or by more loosely coupling L2, and by -making this coil larger we can increase the leakage inductance to any desired amount withoutI having any physical coil, as represented by L3.
  • the grid energy of tube VT4 may now be further phased in the same direction by the series resistance R8.
  • Control tube VT4 is provided with the usual supply voltage, its inner grid being given a normal bias of approximately -6 volts by connecting its cathode to the bleeder resistor 51 at a point approximately this number of volts above ground.
  • V This permits the operation of the tube at the mid-point of its control range, as determined by plotting a curveofgrid bias against oscillator frequency which results in an S-shaped curve, so that we secure operation about .the mid-point thereof.
  • the voltage generated by the sweep oscillator I4 is arranged to be a total peak-to-peak of 6 volts so that the effective voltage at the grid of control tube VT4 from the sweep oscillator is i3 volts.v
  • the voltage swing changes the frequency of the oscillator tube VTS by an amount suflicient to sweep the receiver through a range of frequencies approximately '1% of thev carrier frequencyi
  • the director When the director is rendered operative, in a manner to; ble described, it generates a voltage of :20 volts even on the weakest signal for ⁇ which the system is designed.
  • This voltage is suicient to overpower the sweep voltage and
  • This core is preferably of similar coni to tune the receiver tothe incoming carrier within approximately 1 kilocycle,
  • the means for rendering the director operative upon the reception of ⁇ a carrier modulated by the proper tone frequency comprises the switching tube VTIO which is energized by the tone lter I'I or II' (Fig. 1).
  • This filter comprises an amplifying tube VT8 whose grid is conneoted to the audio amplifier through a small condenser CI and the coupled resonant circuits TC3 and TC4 which may be permeability tuned to the desired tone frequency, as indicated at 5B.
  • the identifying tone frequency is within the preferred range of from 4000 to 20,000 cycles, each of these circuits is tuned to that frequency.
  • the selected tone frequency voltage is amplified by tube VT8 in a resistance coupled stage and rectified by the circuit including the diode 54, 55 and resistor RII, one end of which is grounded.
  • the grid of the audio output tube VT9 is normally biased to -10 volts by means of the self-biasing resistor G9 which is shunted by a condenser l'10.
  • This arrangement provides a normal negative voltage of -10 volts on the plate 54 of the diode with reference to its cathode 55. A signal must, therefore, develop a potential on the positive peaks in excess of the 10 volts negative bias in order to permit the diode to rectify.
  • a weak desired signal which may, for example, be modulated at a tone frequency of 5000 cycles for purposes of station identification, be scanned by the action of the oscillator I2, control device I3 and sweep oscillator I4, and in about 3 milliseconds builds up in the resonant circuits TG3 and TC4 to approximately full amplitude.
  • This voltage is amplied by tube VT8 and impresses substantially 20 volts positive peak voltage on the diode plate 54, thus overcoming its 10 volts negative bias and producing a rectified output voltage across RII of the order of 10 volts.
  • This voltage is filtered by the filter circuit comprising resistor RI2 and C8 and will be hereafter referred to as the switch operating voltage.
  • This voltage is sucient to override the sweep voltage developed by the sweep oscillator I4 and lock the receiver on the carrier.
  • the noise voltages appearing in the director line 58 are preferably filtered out by the filter circuit which comprises the internal resistance of the director device which is about 2 megohms, and the condenser C4 which has a capacity of 0.5 microfarad.
  • both the tone and the carrier must be present to maintain this condition. If either one disappears for more than a few milliseconds, the director driver tube VTI becomes blocked so that no director voltage is developed and the receiver instantly resumes the scanning condition under the control of the sweep oscillator I4.
  • the voltage developed by the circuits TO3, TC4 as determined from their combined selectivity curves at 6000 cycles is only about one-tenth of that developed at their resonant frequency of 5000 cycles. But this voltage difference in itself would be insufcient to prevent the development of an effective switch operating voltage which might lock the receiver on an undesired carrier which may be 100,000 times stronger.
  • One of the means which has been found effective to prevent the development of the switch operating voltage for an undesired carrier comprises the tube VTI, the constants of this tube and its associated circuits being designed so that the maximum power developed in its plate circuit is substantially milliwatts.
  • the sweep oscillator I4 and its associated filter circuit comprising RI and C4 illustrated develops a substantially sine shaped voltage wave to effect the scanning action, but it will be understood that a source which generates a voltage wave of other desired shapes such as triangular, sawtooth, etc., may be used instead.
  • the general B-I- supply is 250 volts.
  • Vacuum tubes of the following types are found suitable for use with the circuits described:
  • this tuning is effected by manual adjustment of the permeability tuning means 4 which is unioontrolled in any known manner with the tuning means B5 of the oscillator.
  • a tone switch operating voltage is developed across the diode resistor RI I which is suiiicient to substantially block the tube VTIIl. This action causes the voltage of screen'SI to rise very substantially, so that the plate current of VTI energizes the director VT2, and a minimum director voltage of $20 volts is developed and through line 58 is applied to the control grid of the control tube VT4.
  • This high voltage overpowers the control voltage of i3 volts developed by the sweep oscillator and serves to maintain the reactance of the controlk tube at a substantially constant value, thereby maintaining the oscillator frequency at a substantially constant value which heterodynes with the carrier frequency to produce the proper beat frequency which lies within the band of frequencies passed by the intermediate frequency amplifier 6.
  • the receiver remains locked on the carrier as long as the tone modulated carrier is received. If the carrier disappears, no voltage is supplied through line 59 to energize thev director with the result that no director voltage is developed and the receiver resumes the scanning condition under the control of the sweep oscillator M.
  • a receiver of this type When a receiver of this type is to be used in point-to-point communication where there is no possibility that the carrier wave will seriously weaken once contact has been established, it is perfectly feasible to operate the receiver in the tone lock, carrier hold condition. In this condition the tone is impressed on the carrierl only for a second or so to be sure the receiver has had time to lock on the designated carrier, and the tone is then removed leaving the receiver locked on the carrier. Means for doing that include the connection 'II and the switch SWI. Upon closure of this switch the receiver is placed in the tone lock, carrier hold condition, since any negative voltage developed across RI will be applied to the grid of VTIEI, the switch tube.
  • the apparatus in which the invention was developed was a double detection type superheterodyne with a first intermediate frequency of 17.5 megacycles and a nal intermediate frequency of 0.46 megacycle.
  • a radio receiver comprising, in combination, a signal reproducing means, an input portion receptive to signal modulated carrier waves of a single predetermined frequency transmitted from any one of a plurality of transmitting stations and indicating means other than said signal reproducing means coupled to said receiver and responsive to modulations other than the signal modulations on the received carrier for indicating the identity of the transmitting station, said indicating means comprising a member selectively adjustable between an initial position and a plurality of terminal positions and means responsive to the disappearance of the carrier for automatically returning said member from a terminal position to its initial position.
  • a radio receiver having an input portion receptive to signal modulated carrier waves of a single predetermined frequency transmitted from any one of a plurality of transmitting stations, indicating means coupled to said receiver and responsive to modulations on the received carrier for indicating the identity of the transmitting station, an alarm device, means connected to said receiver and responsive to a received carrier for causing the operation of the alarm device, and means responsive to the disappearance of the carrier for restoring the indicating means to its initial condition.
  • a radio receiver having an input portion receptive to signal modulated carrier waves of a predetermined frequency transmitted from any one of a plurality of transmitting stations, a signal reproducing device responsive to the signal modulations continually coupled to the output of said receiver, a sound producing device, means connected to said receiver to automatically cause said sound producing de- Vice to become operative upon the reception of carrier current in the input portion of the receiver, a tone filter electrically connected to said receiver and means responsive to the passage of current through said tone filter to automatically render said sound producing device inoperative.
  • a radio receiver adapted to receive speech modulated carrier waves, said receiver comprising in combination, a translating device for reproducing the speech modulations, a movable switch arm, and a circuit arranged vto connect the output of the receiver to said translating device, said circuit including a portion having one end thereof continuously connected to the output of the receiver and its other end to said movable sWitch arm, said switch arm being normally positioned so as to disconnect the translating device from the output of the receiver and means connected to the receiver and responsive to a single tone modulated carrier impulse for moving the switch arm from its normal position into position to connect the translating device to the receiver.
  • a radio receiver adapted to receive signal modulated carrier waves and having an output circuit, a translating device arranged to reproduce the signal modulations, a movable member connected to said output circuit and adjustable between an initial position and at least two other positions, a circuit arranged to connect the translating device to said movable member in response to the adjustment of the movable memberinto either of said otherV positions and means responsive to modulations on a received carrier for selectively adjusting the movable member from its initial position to either of said other positions.
  • a radio receiver adapted to receive signal modulated carrier waves comprising, in combination, a circuit tunable over a range of frequencies, means for automatically tuning said circuit over the frequency range, means responsive to the reception of modulation on a carrier having a frequency within said range for rendering ineifective the action of said automatic means on the tuning of said circuit, a signal reproducing device and means responsive to modulations other than the signal modulations on a received carrier for selectively causing the signal reproducing device to remain inoperative or to cause it to reproduce the signal modulations on the carrier.
  • a radio receiver of the superheterodyne type adapted to receive signal and tone modulated carrier waves comprising, in combination, a rst detector, an oscillator, means for automatically varying the frequency of the currents generated by said oscillator, means responsive to the tone modulations on a received carrier for rendering ineifective the action of said automatic means on the oscillator, a signal reproducing device and means responsive to modulations other than the signal modulations on a received carrier for selectively causing the signal reproducing device to remain inoperative or to cause it to reproduce the signal modulations.
  • a radio receiving system for receiving signal and tone modulated carrier waves comprising at least two radio receivers of the superheterodyne type, each of said receivers comprising, in combination, a rst detector, an oscillator, means for automatically varying the frequency of the currents generated by said oscillator, means responsive to the tone modulation on a received carrier for rendering ineffective the action of said automatic means on the oscillator and a signal reproducing device; means responsive to a predetermined number of modulations on a received carrier for causing the signal reproducing devices of all the receivers to reproduce the signal modulations on the carrier and means responsive to a different number of modulations on the carrier for causing the signal reproducing device of only one receiver to reproduce the signal modulations on the carrier.
  • a radio receiver adapted to receive signal modulated carrier waves and having an output circuit, a translating device arranged to reproduce the signal modulations, a movable member connected to said output circuit and adjustable between an initial position and at least two other lating device to said movable member in response to the adjustment of the movable member into either of said other positions, means responsive to modulations on a received carrier for selectively adjusting the movable member from its initial position into either of said other positions and means for automatically returning the movable member to its initial position in response to the disappearance of the carrier.
  • a radio receiver comprising, in combination, a signal reproducing means, an input portion receptive to signal modulated carrier Waves of a predetermined frequency transmitted from any one of a plurality of transmitting stations, a plurality of spaced contacts, an alarm device positions, a circuit arranged to connect the transconnected to a rst of said contacts, an indieating device other than the signal reproducing means connected to a second of said contacts and adapted to indicate the identity of a transmitting station, a switch blade movable along said contacts and normally positioned on said rst contact, means responsive to the reception of a carrier Wave to automatically cause the operation of said alarm device While said switch blade is on said first contact and means responsive to modulations on the carrier to advance said switch blade from said rst Contact onto said second contact to thereby cause the operation of said indicating device.

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  • Selective Calling Equipment (AREA)
US321379A 1940-02-29 1940-02-29 Method and apparatus for radio receiving Expired - Lifetime US2300081A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
FR882609D FR882609A (fr) 1940-02-29
NL65298D NL65298C (fr) 1940-02-29
US321379A US2300081A (en) 1940-02-29 1940-02-29 Method and apparatus for radio receiving

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US321378A US2283523A (en) 1940-02-29 1940-02-29 Scanning radio receiver
US321379A US2300081A (en) 1940-02-29 1940-02-29 Method and apparatus for radio receiving

Publications (1)

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US2300081A true US2300081A (en) 1942-10-27

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US321379A Expired - Lifetime US2300081A (en) 1940-02-29 1940-02-29 Method and apparatus for radio receiving

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US (1) US2300081A (fr)
FR (1) FR882609A (fr)
NL (1) NL65298C (fr)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2467564A (en) * 1944-10-13 1949-04-19 Hazeltine Research Inc Wave-signal receiver, including a disabling arrangement
US2523315A (en) * 1947-06-06 1950-09-26 Farnsworth Res Corp Selective calling system
US2533662A (en) * 1947-04-11 1950-12-12 Automatic Elect Lab Automatic trunk selecting system for radio telephone stations
US2863044A (en) * 1954-04-21 1958-12-02 Gen Motors Corp Sensitivity control for signal seeking tuners
US4190838A (en) * 1978-07-20 1980-02-26 R A Electronics, Inc. Radiation detector
US5448755A (en) * 1991-05-07 1995-09-05 Matsushita Electric Industrial Co., Ltd. Oscillation scheme for a selective calling reception apparatus

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2467564A (en) * 1944-10-13 1949-04-19 Hazeltine Research Inc Wave-signal receiver, including a disabling arrangement
US2533662A (en) * 1947-04-11 1950-12-12 Automatic Elect Lab Automatic trunk selecting system for radio telephone stations
US2523315A (en) * 1947-06-06 1950-09-26 Farnsworth Res Corp Selective calling system
US2863044A (en) * 1954-04-21 1958-12-02 Gen Motors Corp Sensitivity control for signal seeking tuners
US4190838A (en) * 1978-07-20 1980-02-26 R A Electronics, Inc. Radiation detector
US5448755A (en) * 1991-05-07 1995-09-05 Matsushita Electric Industrial Co., Ltd. Oscillation scheme for a selective calling reception apparatus

Also Published As

Publication number Publication date
NL65298C (fr)
FR882609A (fr)

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