US2357398A - Transmitter having impulse modulation - Google Patents

Description

Sept. 5, 1944. RME-GRAY 2,357,398

y TRANSMITTER HAVING IMPULSE MODULATION y Filednec. 19. 1941 FIG.

Patented Sept. 5, 1944 Richard Edmund'Gray, London, England, assignor to International StandardY Electric Corporation, New- York, N. Y

Application Deceinhenll), 1941, ServialN-o. 423,634 In France April 1, 1940 (Cl. Z50-17.)

Claims.

y The present invention relates to impulse modulated transmitters which areparticularly applicable to telegraph systems that use impulse modulation.

The main object of the invention is the providing of transmitters for impulse modulation systems that are sturdy, that occupy little space and that do not comprise thermion'ic tubes.- Such transmitters are specially suitable for use asportable senders of telegraphic signals.

An impulse modulated telegraph sender that incorporatescharacteristic features of the invention is disposedso as to emit starting and terminating impulses of signalsthat consist of wave trains produced in an oscillatory' circuit associated with the radiating antenna, th'e'impulses' being generated by a manipulation eifected'on the oscillatory-circuit. f

According to another characteristic featureof the-invention, the manipulation may be manual an'dmay be applied to the oscillatory circuit, either manually or by meansl ofy a'- relay! located in a vacuum. ,v l

According to another feature of the invention, means are provided for changin'g'the',Wavelength of the 'starting and terminating impulses iii-such a way as to insure'greater4 independence of the interferences in the radio connection, and' a greater secrecy of the signals atv the same time'.v In yone example of an embodiment, a tubeles's transmitting device for an impulse modulated telegraph system comprises a two-way keywhich, in one position, controls the connectionof a condenser in an emitting antenna oscillatory circuit (comprising an inductance andA this condenser) and another condenser of the same value in aghigh frequency charging circuit, the connections of the two condensers being reversed in theother position of the Ykey. The'discharges of the condensers send the brief starting and terminating impulses of each signal intovthe antenna and, if desired, the relative capacities of the condensers may be regulated in order to insure afdnite change of frequency between the said starting and terminating impulses; r y

The invention will be explained in rdetailin the following description of examples ofemb'd'i'fnent vantageously in the circuit'sof' the` transmitters of' Figs. 1 and2.

a way thatisexplained'further on; An antenna 'lois directly branchedv at suitable points of the inductance 4; A source of high voltage 8 is'r connected between contact 3 of key l and an intermediate point of the'connection that'permanently couples inductance 4 to the' two condensers 5 and 6i The vmode of'operation caribe explained as follows: In'oneof its positions,A key'l connects one orA other of condensers 5 and 6" to the indl'ictance 4v andconnects the other-condenser to the high'voltage source-l.` In the position shown in the drawing, forA example, rkey I connects at its'contact 2 Vthe condenser 5 in closed circuit with the inductance 4,;wl'i`1e atits contact 3 it connects condenser Iitol theAv terminals of the high voltage source V8;A In this way, conderisery S-is charged almost instantaneously over" the source tlg-while condenseris' discharged over inductance 4iV In the otherposition of the key,- tliefcorinections of vcondensers 5 and 6 Iare reversed, and it is condenser 5 that is charged bythe source 8, while condenser ll is discharged into inductance 4. Inductance l and condenser 5" or 6j that "is vr`connected'tof it constitute a high frequency' circuit that is'L tuned tothe desired' frequencyor trailsmission. The oscillatory dischargeY of the condenser over the'vin'ductance sendsout a 'liiglfi frequency energy impulsev which is radiated vby the antenna'y T. I Y 1 It can thus be seen that annimpulse is sent withr` each change ofv position-.of key"` so that manipulation of the key upward and downward, or'viceA versa depending onthe' normal position, causes the sending 4of a pair of impulses'spaced in time and of the duration required'fo'r marking afdot or a dash.A These impulses consequently define'V the beginning and termination 0fl each telegraphic signal. A I

Thevr emitted signalscan berce'ived' with l'any receiver adapted 'to receive y impulsefmodulated signals.v Receivers of this kind are well known per se andV do not call Vfor 'ayparticular description. Y

It is evident that if it is desiredto maintain a certain amountof secrecy, or` only to 'increase the independencey withY respect* to 'the interferences that vclar'acteri'z'e impulse modulation? sys- 'p 'pa-'irl maybe" tr" "I mitteczlona diirereittfrequencyby select gun- 'egualj values'jfo' condensers 5`fand 6r iin affp're'determined ratio; .Y f f Fig.' 2 illustrates" a modification offthelcircuit of *'Fig. '1 in v i rhi`cl"1` key lt isfreplacedjbya two contact relay l U,- the operation Vpf' whiclrfeff'ec'zts the relay is placed in an extreme vacuum, such as an electron discharge tube vacuum in order to avoid sparks and its contacts when it is operating. It is controlled, as shown, by a simple manual key II that is inserted in its exciter circuit. The' installation of relays of this kind in a vacuum...V

is known per se and is consequently not describedv j in detail.

The high voltage source 8 of Figs. 1 and 2 may'v be of any suitable kind. However, in order to have the entire apparatus retain the advantages ling source, said condensers and said inductance that in ea-ch position assumed by said signalling A means, one pre-charged condenser is connected directly to at least a portion of said inductance to Y form an oscillatory circuit, whereby the respective reactances of said condenser and said portion of said inductance determine the periodicity of the of simplicity it enjoys from the above described- A arrangements, it is preferable to provide this source as a high voltage vibratory system fed by a low voltage battery. Figs. 3 and 4 show two examples of known circuits of this kind of high voltage feeding systems, and these can be used directly in transmitters such as those described above, the terminal I2 of each of these circuits being connected to contact 3 of key I or relay I0, and the terminal I3 of these circuits to the point of permanent connection of source 8 to the oscillatory circuit.

In the circuit of Fig. 3, a low voltage battery I 4, e. g. of 6 volts, has its direct current transformed into alternating current by the vibrating contact I5, and this alternating currenty has its voltage increased by the transformer I6 whereupon it is rectified by the diode which recties the two alternations I1 and which has its plates connected to the two ends o f the secondary of transformer I6. The rectified high voltage current is transmitted through a filter I8 to the terminals I2 and I3 to which 'the circuit of the described transmitter is connected. n

The equal resistances IS-IS' and the condenser are provided for the purpose of preventing sparks at the vibrating contact I5, while the` condenser CI v is provided for absorbing transient currents that might cause interferences in the output current.

The circuit of Fig. 4 illustrates a simpler form of thepvibratory high voltage source. The current of battery 2l is transmitted to a vibrating armaf ture 22 which is provided with two pairs of contacts that are respectively connected to the ends of the primary and secondary windings of the stepfup transformer 23, so that the direct current of battery 2 I, after having been transformed into alternating current and raised in voltage, is immediately rectied inthe secondary of the transformer. After filtering in 24, this high voltage rectified current is applied to the terminals I2 yand I3 and consequently to the oscillatory circuit of Figs. 1 and 2.

Although the invention has been described for the particular case of certain examples of embodiment, it is evident that itis by no means limited to the same, particularly as regards the actual form of the control key of the oscillatory circuit and the high voltage feed of this circuit. It is, on the contrary, capable of numerous modiiications and adaptations without departing from its scope.

What is claimed is:

1. Radio transmitter for producing signals defined by. the lapse of time extending from the transmission cfa first single train of damped osance having a predetermined reactance, means for producing in said inductance both said rtrains nfirst train of damped oscillations resulting from said connection, and at the same time the recillations to the transmission of a second single train of damped oscillations, including an inductf maining condensers are connected to said charging source, said signalling means being likewise connectedso that the assumptionv of anotherv position thereby will cause the connection to said inductance of a second pre-charged condenser, so as to produce in the oscillatory circuit formed .thereby a second train of damped oscillations, of a periodicity likewise predetermined by the respective reactances of said second condenser and said portion of said inductance to which it is connected, the time elap'sing between successive positions of said signalling means being under manual control and being variable in extent, whereby a predetermined signal may be transmitted.

. 2,.,Animpulse modulated transmitter according to claim 1, wherein said signalling means comprises a vacuum relay and also including a manually operable signal key so connected as to control the actuating circuit of said vacuum relay.

3. An impulse modulated transmitter according to. claim 1, wherein said first and second condensers yare of different capacities, whereby the respective shockV excited damped periodic oscillations constituting the starting and terminating impulses, respectively, of a signal are of different frequencies.

r,4. An impulse modulated transmitter in which the signal elements are defined in duration by starting and terminating impulses, comprising an inductance, first and second condensers, a charging voltage source for said condensers, a connection from one end of said inductance to one armature of each of said condensers, a connection from one terminal of said voltage source to both said last mentioned condenser armatures, and a two position switching device which in one position connects the other end of said inductance to the other armature of said rst condenser and connects the other terminal of said voltage source to the other armature of said second condenser and which in the other positionrconnects the said other end of said inductance to said other armature of said second condenser and connects the said other terminal o f said voltage source to the said other armature of said first condenser, and whereby said rst condenser connected to said charging source acquiresa static charge and upon connection to said inductance, discharges therethrough so as to producea first train of damped waves constituting said starting impulse and having a periodicity predetermined by the electrical constants lof said condenser and said inductance, the connection of said second condenser in like fashonstosaid inductance producing a second similarly determined train of waves constituting Vsaid'terminating'impulse, the time consumed in moving said switching device from one position to the other being under manual control so as to Q'dene a signal by temporal' characteristics, said transmitter also including means for transferring said respective trains of damped waves from said transmission purposes, and connection means bel0 tween said key and said inductance for connecting, in each key position, a single pre-charged condenser in shunt to at least a portion of said inductance so as to form an oscillatory circuit of a frequency determined by the reactance of the elements thereof, whereby a damped pulse of oscillatory energy occurs when said key makes contact at each position thereof.

RICHARD E. GRAY.

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