US2415727A - Radio transmitter - Google Patents

Description

Feb 11, 1947. c. P, CLARE RADIO TRANSMITTER Filed May 20, 1944 2 Sheets-Sheet 1 Feb. l1, 1.947.

C. P. CLARE RADIO TRANSMITTER Filed May 20, 1944 2 Sheets-Sheet 2 N ma m M JTWH m ,lmllw @5 M `Patented Feb. 11, 1947 UNITED srATcs nanro 'massi/narran Carl l. Clare, Arlington Heights, Ill., assignor to C. P. Clare and Co., Ghicago, Ell., a corporation of Illinois Application May 20,` 1944, Serial No. 536,584

4 Claims.

My invention relates broadly to remote control systems and more particularly to a system for transmitting warning signals in remote control systems. ,l

This application is a continuation in part of my application Serial No. 373,173, filed January 4, 1941, now Patent 2,355,055, issued August 8, i944, for Electric relay system.

One of the objects of my invention is to provide an electric relay system for operation in a remote control system by which various circuit permutations and combinations may be effected and in addition a repeating warning signal may be controlled by the relay system.

Another object of my invention is to provide a local and remote control circuit for a radio transmission system by which the radio transmitter may be operated from a remotely controlled location for transmitting a warning signal preceding a radio transmission by voice modulation or other means.

Still another object of my invention is to provide a remote control system for radio signaling systems whereby composite signals may be transmitted over desired time sequences by a radio transmitter that is remotely controlled from a supervisor position.

A further object of my invention is to provide a control circuit for a remote control system capable of establishing three different circuit conditions over a control line by displacement of a control key or switch to either of three selective positions.

Other and further obje-cts of my invention re.- side in an arrangement of electric relay system having means for controlling the operate and release time of the magnetic system of a relay system as set forth more fully in the speciiication hereinafter following by reference to the accompa, .og drawings, in which:

Figure l is a schematic wiring diagram showing the remote control system of my invention for distant control of a radio transmitter whereby a warning signal may be transmitted from the radio transmitter to signify the commencement -of a broadcast followed by the desired broadcast in desired sequence; Fig. 2 schematically illustrates the circuit condition at the controlling station when the control key or switch is manually held in dial position; Fig. 3 schematically illustrates the circuit condition when the control switch Vor key is moved to locking ring position; Fig. 4 schematically shows the circuit condition when the control switch or key is in locking neutral position; Fig. 5' shows a characteristic curve for the electric relay system used in the remote control system of my invention in which the electrical operating time of the relay system is regulated in accordance with the principles of my invention; and 1Eig. 6 shows a characteristic curve in which both the electrical and vmechanical characteristics of the relay system are controlled for securing the repeat signal operation required as a warning signal in the remote control system of my invention.

My invention provides a method of remote control for a radio broadcast transmitter or other signalling system for transmitting a warning signal in advance of a broadcast. The system of my invention is particularly applicable in aircraft traffic control and navigation systems in whichv an operator in a remote position with respect to a transmitting ground station desires to notify aircraft that a broadcast is about to commence. The operator in the remote control station is provided with a three position switch or key having a manually actuated dial position, a locking ring position and a locking neutral position. The operator may manually move the control switch to dial position and dial a particular digit on the remote control mechanism at the control station and then quickly shift the control switch or key to ring position and allow the switch or key to remain locked in ring position and in accordance with the system of my invention effect the transmission of warning signals at a rate of approximately eight per second on any selected audio tone frequency such as 1,020 cycles. The warning signals at 1,020 cycles are transmitted so long as the control operator allows the control key or switch to remain in ring position, thereby advising the pilots of aircraft that a broadcast is about to commence. The operator may then shift the key or switch to neutral locking position and control the modulation circuit of the distant radio transmitter either by voice or telegraph signals. The control switch or key is always ready for a repeat control operation, the important sequence being the movement of the control switch or key first to dial position for effecting a selection of the connection between the warning circuit and the modulation circuit of the radio transmitter. Such selection when once established is not disturbed by quick movement of thfe control key or switch to ring position because of the time relay characteristics of the relay circuits employed between the control circuit and the selecto-r apparatus and the almost innitesimal interruption of the control current. This method of transmission has proven highly effective in the transmission of weather, emergency warnings, traffic, and other information to aircraft in a particular area. However, my invention is not limited to this particular application and is applicable to signalling systems generally in which a calling signal of predetermined characteristic is to be transmitted in advance of the signalling operation. My invention also has application to the transmission of signals of particular tones for controlling of start-stop functions for the motor circuits of facsimile and printing telegraph systems and forthe starting through audio frequency transformer I to the Y contacts of the control key I8 for controlling connections to the line system I3. The control key I8 is indicated generally as having a dial position I9 and a ringing position 20. The dial switch control device at the remote control station is indicated at I6.A The signalling circuitl is indicated at II having leads LI and L2 normally connected through key I8 to the line I3. The operator at the remote control station by moving key I8 to the dial position i9 and operating the dial I6 opens and closes the circuit over line I 3 for transmitting impulses to the controlled station. At the controlled station relay A--4 |96 follows these impulses and through-its back contact I causes the motor magnet I0 through intermediate relay B-4I96 to actuate the stepping switch 2 l22 the specic number of steps corresponding to the impulses transmitted from the dial through any suitable range such as l', 2' 30. Relay B-4I96 and a cut-out relay D-4ISS are both of a slow release type. The reason for the use of time delay feature in the circuit of my invention is to prevent opening of the contacts in the absence of a control current for a given time period for maintaining the circuit in operation. The innitesimal interruption of currentfrom source I4 in the control circuit upon movement of key I8 from dial position I9 to ring position 20 does not interfere with the maintenance of the selec- -tionA circuit because of the slow release action of relay 13-M96. The intermediate relay B-4I96 duetoits slow release action remains operated after its circuit is rst closed, thus holding its contactsZ-S closed. After the last impulse from the dial, relay -D-MQS, which operated on the first impulse from relay .Ia-M96, due to its slow release action remains operated during the series of impulses transmitted from the dial and restoresand closes a circuit from positive on contact 2 Vof relay A-l I 96 to the primary relay associated with the last stepping relay step. Relay A-4I96 remains energized so long as key I8 remains in dial position after the series of impulses has been-transmitted, in order to maintain the selected primary relay energized, or so long as key I8v remains locked in ring `position for transmitting current from source I4 to the line circuit. Y Thedial position of the control circuit is shown more clearly in Fig. 2 while the ring positionof'the control circuit is shown more clearly in Fig.r3.

Therneutral position for key I8 is shown in Figi. Key I Bis of the cam lever type in which the movement ofthe lever to-which handle of key I8 is attached functions to engage cam members connected with the leaf springs for moving the leaf springs to operating position.

In Fig. 2, for example, wherein the key lever is movedto dial position the lever arm connected with the operating handle of key I8 engages cams 'associated withulever springs 66 and 6l which are connected to the line circuit I3 serving to spread the leaf springs and move them to positions in which they establish connection with contactsto winding I5 of the transformer circuit and through dial switch i6 and resistance III to contact 68 and leaf spring 66 returning to the opposite side of line I3. Leaf spring 66 is associated with pedestal insulator 1I which connects with leaf spring 'I2 for simultaneously moving leaf spring I2. Leaf spring 'l2 when shifted as shown in Fig. 2 establishes connection with contact 'I3 which places warning lamp 14 in circuit with the power supply source from winding I5 of the transformer circuit I 4 thereby indicating to the station operator that key I8 is in dial position.

In the position illustrated in Fig. 3 wherein the lever controlled by switch handle I8 is moved to ring position, it will be observed that leaf springs 65 and 67 have been restored to neutral position and establish connection with contacts 'I4 and 'I5 respectively completing circuits to the lever springs indicated at 'I8 and Tl. The movement of key I8 to the position illustrated in Fig. 3 results in displacement of spring members 'I6 and "I7 to positions establishing connection with contacts 'I8 and 'i9 in circuit with winding I5 of transformer circuit, I4. This results in transmitting current from source I4 to line I3 so long as key I8 remains in the position illustrated in Fig. 3.

When key I8 is restored to neutral position as illustrated in Fig. 4 leaf springs 'IB and 'Il establish connection with contacts and 8I connected to the supervising line circuit through leads LI: and L2 thereby establishing Sonnection with a. signalling circuit or a modulating circuit at the: radio transmitter indicated at 28. y 'Delayed action relay B--MSB prevents any interference with the proper functioning of the control system by prolonging the circuit continuity during transition produced preparatory to control of the system by current impulses transmitted from the control station.

The primary relay operates to close a circuit to the desired control which is required, This control may be the closing of certain amplifier circuits or other desired switching operations. In the particular system illustrated, I have shown the broadcast transmitter as comprising a modulation system 29, an oscillator 3i, a power amplifier 32 and an antenna-ground system 33. A modulation control circuit 28 extends to the modulator 29 and a local microphone 34 is provided in this circuit for any local control which may be required. An audio frequency transformer 21 has its secondary winding connected to modulation circuit 28 and its primary winding connected to the leaf springs 25 and 26 of the spring pile-up 24 of the auxiliary relay 39, The contact springs 25 and 26 move to either of two positions. In the upper position, contact springs and 26 connect with contacts 35 and 3S which connect to the contacts il andI of the contact assembly 23 of relay B--4I96. In the opposite position, leaf springs 25 and 26 connect respectively with contacts 3'! and 38 leading to the tone frequency source under control of the relay system 42 of my invention. The relay 42 comprises the magnetic core 44, the operating winding 43, the slow operate slug 45 for electrically controlling the operating time of the relay and the armature 4t pivoted at 4l. The armature 46 has an operating lever arm 4S integral therewith which controls the operation of the spring pile-up shown at 593. The armature 46 has the inertia device 48 attached thereto for mechanically controlling the operating time of the relay. The spring pile-up 5t includes leaf springs El, 52, 53, 5ft, 55 and 55. The leaf springs El-EZ carry contacts 5la and c2c. which are electrically connected in series with the control winding s3 and with the power source through contact spring liti and coacting contact di of auxiliary relay 39. The relay d2 is thus self- 'interrupting through the cooperation of contacts 5 l a, and in the current path to the rela-y winding d3 at a rate of time depending upon the coaction of the inertia of armature i6 due to the added mass i8 and the iniiuence of the eddy current field produced by slug 45 upon the normal field of winding d3.

A suitable source of alternating current having a tone frequency, for example, oi 1G20 cycles is connected at 5l to primary winding 58 of transformer 59, whose secondary Winding 6E! is connected to leaf springs and 56 of spring pileup 5d. The movable contact springs 52 53 and 55 are interconnected through bushings of insulation material indicated at iii and 52 so that movement of lever arm @s moves leaf spring 52 to open contacts 5to, and 52a, while leaf springs 53 and 55 move to positions in which contacts 53o and a. establish connection with contacts Ella and 5ta, respectively, thus closing the circuit from secondary winding Sil of transformer 59 to the contacts 3l and 38 of spring pile-up 24 of auxiliary relay 3S. I have schematically illustrated the prima-ry relays of the remote control system at E-ill and F-ls and the secondary relays at Cif-ilse I have schematically shown the several contacts and leaf springs for the several re- ,l

lays and control apparatus at i, '2, 3, 4, 5, 6, l', 8 and 9 with polarities indicated to aid in tracing the circuits of the control system.

In the instant case assume that it is desired to broadcast a certain message. The operator moves key it dial position l and dials the digit 3 which causes the stepping switch 2 i-ZZ to step to its third contacts and relay A-lsl to remain energized afterward. Relay D--Llll on restoring after third impulse closes a circuit to primary relay 3. Primary relay 3 closes a circuit to the auxiliary relay 3Q which transfers the circuit from contacts 23 leading to the modulation channel through the primary of the broadcast transformer 2 to contacts 54% and 55 on the weighted armature relay l2 of my invention. The circuit to the winding of the weighted armature relay i2 is also closed by the auxiliary relay. 39 through spring it and contact 4l' and as previously described, the weighted armature relay l2 operates approximately eight times per second to cause a warning i020 cycle tone to be placed on the modulation circuit 23 of the broadcast station. rThis interrupted tone is held on the modulation circuit of the broadcast station as long as the operator at the distant control station allows the key i5 to remain locked in ring position as shown in Fig. 3. After this tone has been held on the desired length of time for transmitting the warning signal the operator restores the key i5 to neutral position as shown more clearly in Fig. l, and the stepping switch 2|-22 restores itself to normal.

The control operator by using key i8 and dial l5 as before, then dials the broadcast number and the Stepping switch Zl-ZZ functions to operate the primary and secondary relays to effect whatever functions they control, with leaf springs 25-26 of Spring pile-up 24@ contacting the contacts and 36 as shown in Fig. l, after which (ill key I8 is restored to neutral as shown in Fig. 4 and the broadcast takes place. Thus a multiplicity of functions may be'controlled over the sameline circuit by selection through the stepping switch mechanism 2 l22. After the warning signals have been transmitted as hereinbefore explained the operator upon moving key i3 to neutral in effect places signaling circuit il in supervisory position through leads Ll and L2 to line I3 and through contacts 4--5 and i-'i and contacts 2li-25 and 3ds-26 to the modulation transformer 2l of the modulation circuit 23 of the radio transmitter. Thus a microphone and power source connected to signaling circuit l1 enables the radio transmitter to be voice modulated from the remote control position. If a sending key and power source is connected to signaling circuit Il or any other form of modulating means employed the modulation circuit 28 of the radio transmitter can be correspondingly controlled.

I have found the relay system of my invention very practical and successful in operation. The mass added by Weight d8 provides the movable armature system with that amount of mechanical inertia which will coact with the electrical inluence introduced by slug l5 to enable operating winding 43 while energized from a continuously applied source to cause the controlled circuit connected through sets of Contact springs 53, 5d, 55 and 55 to alternately connect and disconnect a source of control potential tothe circuit to be controlled. The rate at which this control is applied is readily controllable by changing the character of slug l5 and the effective mass 48.

Figs. 5 and 6 illustrate the efiect of the slug i5 and the weight i8 on the movable armature. in Fig. 5 the curves illustrate the manner in which the flux density increases and decreases in the magnetic system according to time where the flux builds up during the make period of contacts Sia and 52a and decreases to a condition where it commences to increase again before the flux cycle through the magnetic parts has been completed. The iniuence of slug i5 in the eX- ample illustrated is such that the flux cycle increases through a time period represented by a unit of time while the decrease in flux takes place over a fourth of the increase time. The self-interruption effected by the breaking of the circuit through winding i3 by contacts elo and 52a produces a repetition of alternate increases and decreases of the fiuX cycle as illustrated. in order to increase the rate of make and break of the spring pile-up system the mass t is added to armature it with the result shown in Fig. 6. The time period for initial build-up of the inagnetic nur is now one unit of time compared to a tenth of the time for decrease of flux. The ux cycle is not completed but repeats in a series of substantially saw-tooth curves as indicated until the controlling current is removed. During this period the spring pile-up assembly is being functioned through a series of rapid repeating strokes and impresses the characteristic tone frequency from source lil? upon the load circuit or modulation circuit of the radio transmitter illustrated in Fig. l. By proportioning the mass of the movable armature system and the arrangement of slug d5 in the field of winding @l5 a rate of make and break of, for example, eight times per second maybe obtained.

The composite system of control of my invention enables an operator at the remote control station Il vtocontrol the operation of the radio transmitter at the local control station i2 so that voice transmission from the radio transmitter maybe preceded by a warning signal produced by operation of the recycling relay system which may :be controlled sequentially to connect the 1020 cycle tone to the modulation circuit of the transmitter through transformer system 2l. The modulation circuit of the transmitter may be controlled by the supervisor from the remote control station for emitting the desired characteristic of signal and the radio transmitter may also be locally controlled through microphone 34 connected with the voice modulation circuit 28. The slow release relay B-Mt in the control system prevents opening of relay contacts in the absence of a controlled current for a given time (period, thereby maintaining the system in operation. The interruption of the key control circuit i8 does not interfere with the maintenance of a selector circuit because of the slow release action of relay B-MQS.

I realize that various changes may be made in the relay arrangement and while I have described my invention in certain preferred embodiments, I desire that it be understood that modifications may be made and I intend no limitation upon my invention other than may be imposed by the scope of the appended claims.

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

l. A control system for a signal transmission system comprising a transmitting station including a signal transmission system having a local voice modulation circuit, an audio frequency energy transmission channel connected with said local voice modulation circuit, a source of alternating current, a mechanically recycling relay including an operating winding, a movable armature and a multiplicity of contacts controlled thereby, circuits interconnecting said source of alternating current and certain of said contacts, a remote control station including an alternating current control source, a two-position control switch and a dialing switch,-a circuit interconnecting said control source, said dialing switch and one position of said two-position control switch, a signalling circuit connected with the other position of said two-position control switch, a line wire control circuit interconnecting said remote control station 'and said signal transmission system for selectively establishing connection between said rst mentioned source of alternating current and said audioy frequency energy transmission channel and controlling the impression of said mst mentioned source of alternating current upon said audio frequency transmission channel at a rate determined by the operation of said mechanically recycling relay for correspondingly controlling the emission of a sustained signal from said signal transmission system through said local voice modulation circuit.

2. A control system for a signal transmission system comprising a transmitting station including a signal transmission system having a local voice modulation circuit, an audio frequency enengy transmission channel connected with said local voice modulation circuit, a source of alternating current, a mechanically recycling relay including an operating winding, a movable armature and a multiplicity of contacts controlled thereby, circuits interconnecting said source of alternating current and certain of said contacts, a remote control station including an alternating current control source, a two-position control switch and a dialing switch, a circuit interconnecting said control source, said dialing switch and one position ci said two-position control switch, a signalling circuit connected with the other position of said two-position control switch, a line wire control circuit interconnecting said remote control station and said signal transmission system for selectively establishing connectionV between said first mentioned source of alternating current and said audio frequency energy transmission channel and controlling the impression of said rst mentioned source of alternating current upon said audio frequency transmission channel at a rate determined by the operation of said mechanically recycling relay for correspondingly controlling the emission of a sustained signal from said signal transmission system through said local voice modulation circuit, and means connected with said line wire control circuit for delaying the opening of said circuit in the absence oi a controlled current.

3. A remote control system comprising in combination a remote control station and a local control station, a line wire circuit interconnecting said stations, a controlling source at said remote control station, a signal transmitter at said local control station, a mechanically recycling relay at said local control station, a source of a1- ternating current connected with said mechanically recycling relay, a voice modulation circuit connected with said signal transmitter, and means operated from said remote control station for directly controlling said voice modulation circuit of said signal transmitter or conditioning said mechanically recycling relay for periodically impressing the source of alternating current at said local control sta-tionupon the voice modulation circuit of said signal transmitter over a predetermined time interval.

4. A remote control system comprising a transmitting station including a signal transmission system having a local voice modulation circuit, an audio frequency energy transmission channel connected with said local voice modulation circuit, a mechanically recycling relay including an operating winding, a movable armature and a multiplicity of contacts controlled thereby, a tone frequency source connected with said multiplicity of contacts, means for completing a circuit between said local Voice modulation circuit or between said local voice modulation circuit and said audio frequency energy transmission channel, a control station, an audio frequency source and a signal circuit at said control station, and a selector switch at said control station for rendering either said signalling circuit or said audio frequency source at said control station effective over said audio frequency energy transmission channel for selectively controlling the connection of said mechanically recycling relay or said audio frequency energy transmission channel to said local voice modulation circuit.

CARL P. CLARE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,250,950 Goldsmith July 29, 1941 2,064,958 Taylor et al. Dec. 22, 1936 1,945,082 Sandeman et al. Jan. 30, 1934

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