US2134562A - Signature keying device - Google Patents

Description

Patented Oct. 25, 1938 SIGNATURE KEYING DEVICE William Kimmich, Flushing, N. Y., assignor to Radio Corporation of America, a. corporation of Delaware Application April 3, 1937, Serial No. 134,826

7 Claims.

This invention relates to signature keying devices for multi-channel carrier wave systems. More particularly my invention has to do with a means providing a remote start-stop control tone modulation to be used on a radio communications system, such a tone constituting a source of signature impulses which may be transmitted additionally to the start-stop signals.

Ultra-high frequency radio communications networks have been put into commercial use under conditions which enable the carrier wave to be modulated by different tone frequencies, eachtone frequency being itself a carrier for a certain traflic communications channel or for a remote control tone frequency channel. Under the requirements of the Federal Communications Commission it is necessary that allotted frequency bands be identified by periodic announcements of the signature or signatures of each transmitting station; These'signatures may be announced orally or by means 'of Morse code signals.

It is an object of my invention to provide a system whereby Morse code signatures may be impressed upon a tone modulation and then upon an ultra-high frequency carrier wave for radio transmission. 7 c a It is a further object of my invention to provide an automatic code call signalling device for intermittently and successively keying a number ofdifferent signatures. Each of these signatures usually identifies one of a plurality of radio transmitters in a concatenated network, such as required for ultra-high frequency transmission over distances greater than the working range of a single transmitter, f Preferably the time occupied by the transmission of the signature is made of lesser duration than the time intervening between successive signatures and all of the different signatures are caused to be transmitted one after another before a given signature is repeated.

Further objects and advantages of my invention will become apparent upon review of the following detailed description taken in connection with the accompanying drawing, the sole figure of which shows diagrammatically a preferred embodiment of the apparatus to be used at a terminal' sta tion for; traific keying as well as for remote start-stop control signalling and signature signalling- Referring to the drawing, I show an ultra-high frequency generator 3 feeding into a transmitter .4, the output energy from which may be radiated from any suitable antenna 5. The ultra-high frequency carrier wavefrom the generator 3 may be simultaneously modulated, if desired, by different tone frequencies as obtained in respect to the different tone generator sources such as those representedat 6, 1, 8 and 9 respectively. The tone sources I, 8 and 9 mayeach be keyed on and off by means of terminal equipment of any preferred type, such equipment being here conventionally shown as keyers for channels A, Band C. The tone source 6 is controlled by an on-and-off switch Hi. The function of this tone source 6 is 10 first of all to operate an on-and-ofi' switch at the station to be called. The practice is to maintain a receiver in constant operation at each terminal station'and at each relay station between the terminal stations. These receivers possess output circuits and filters responsive to a desired calling tone frequency. In the output circuit of the filter is a relay which is rendered operable upon reception of the calling tone frequency. When operated the relay starts up the necessary trans- 2O mitting apparatus or terminal equipment, as the case may be, in order that communication may be established between a sending station and an ultimate receiving station. Frequently the traffic signals to be transmitted will be caused to actuate a printer 'or a facsimile recorder. Different communications may be transmitted simultaneously as on channels A, B and C respectively by means of the keyers I], I2 and I3. Each of the communications as thus keyed will be characterized as modulations of a diiferent tone frequency. These tone frequencies are filtered by any suitable filter means such as those shown at l4, I5 and I6 respectively so that the output modulations from these filters may be impressed upon the carrier wave and sent out by the transmitter 4 from the antenna 5.

In order to satisfy the requirements of the Federal Communications Commission as before mentioned, I have resorted to automatic code call transmitting devices for intermittently keying the tone source 6 with Morse code impulses. Due to the fact that the range of transmission in an ultra-high frequency system is quite limited, it becomes necessary to employrelay stations which are relatively near to one another in order that messages may be sent for any considerable distances. Thus, when a communication channel has been established by starting up the repeaters at different relay stations, the same traflic will be transmitted and re-transmitted over a radio chain, and since diiferent carrier frequencies are generally utilized from point to point, the signature codes for each transmitter must be announced periodically. Each of the si natures represents, then, the call letters either for the terminal transmitter or for one of the intermediate relay transmitters. However, these call letters may all of them be sent out at one station, namely, the terminal transmitter station.

One embodiment of apparatus for transmitting these call letter signatures is herein shown to include a code disc I! which is continuously rotated by a motor l8. The motor itself is provided with a gear reduction so as to rotate the code signalling disc relatively slowly. In one embodiment which has been adopted the motor runs at 1800 R. P. M. and the gear reduction is such that the disc I"! rotates a fraction more than 3 R. P. M. This allows at least 20 seconds for the transmission of a given signature which may be composed of dots and dashes of the Morse code. The keying of these dots and dashes is obtained for any one signature by opening and closing the contacts I9 in response to the notches cut in the periphery of the code disc II. The keying system is clearly evident from the fact that one of the contact springs I9 rests upon the periphery of the code wheel l1 and is caused to make contact with its companion contactor at all times except when it is allowed to drop into a depression in the code wheel periphery,

In the embodiment of my invention as herein illustrated three code signatures are capable of transmission with intervals being interspersed for the uninterrupted transmission of the tone frequency of the remote control start-stop channel. It has been found advantageous in the system .herein described to operate these start-stop controls through relays which have a relatively slow release characteristic so that they will not respond to the interruptions of the tone frequency which are occasioned by the transmission of the Morse code signals. In other words, the holding relays at the receiving station will be maintained locked up as long as the tone frequency from the source 6 at the transmitter is impressed upon the carrier. If, however, the transmitting station is shut down the opening of the switch Ill interrupts the transmission of this tone frequency through the filter 20 and the relays at the receiving station are released for shutting down the terminal equipment at the receiver.

The method herein shown for transmitting different call signals in succession is one wherein the contacts l9 are shunted by closed contacts 2| during the entire long interval between the transmission of successive signatures. The contacts 2| are controlled by a cam 22 having on its periphery a recessed portion which occupies preferably an angle of a fraction more than 5| degrees. The cam 22 is rotated three times during seven revolutions of the shaft 23. This is accomplished by means of a gear ratio of 3 to '7 between the gears 24 and 25, the gear 24 being mounted on the shaft 23 and the gear 25 being mounted on the same shaft with the cam 22. Using these gear ratios I am enabled to open up the contacts 2| for periods of time just sufficient to transmit one of the signatures which occupies a third of the periphery of the code wheel I1. While the contacts 2| are closed, however, for y ths of a revolution of the cam 22 there is an uninterrupted transmission of the tone frequency through the filter 20. With each successive closure of the contacts 2| however, a different signature is transmitted because the code wheel I! occupies one of three positions at the instant when the contacts 2| are closed due to the fact that the gear ratio provides a least common multiple of 2| between the number of revolutions of the code wheel H and the cam 22 respectively.

In the operation of my invention it is possible by using such speed ratios between the code wheel I7 and the cam 22 to divide the channel-time of the tone frequency transmission from the source 6 so that only th of this time will be occupied by signature transmissions, while for the other ths of the time the pure tone frequency will be transmitted. Assuming now that each new signature identifies one of the'three radio transmitters making up the ultra-high frequency network, it will be evident that, as the code signal spread over one-third of the periphery of the code wheel ll travels under the rider contact l9 while the contacts 2| are open, this signature, say for transmitter station #1, will be transmitted. Then, during two complete revolutions of the code wheel i"! no signatures Will be transmitted because of the closure of the contacts 2|. Next, a different portion of theperiphery of the code wheel will present itself to the rider contact I9 for transmission of the signature corresponding to station #2 while contacts 2| are again opened. Finally, as the code wheel and cam continue to rotate, the signature corresponding to station #3 will be transmitted. During all of this time the code wheel IT has made seven complete revolutions and the cam 2| has made three complete revolutions so that they are again in the same relative positions as at the start, for repeating these signature signals.

It will be understood by those skilled in the art that many modifications of my invention may be made without departing from the spirit thereof as herein shown and described. I do not, therefore, wish to be limited except according to the scope of the claims.

I claim:

1. In a code keying system for the transmission of a predetermined signature, a set of contactors, a code wheel having a periphery engageable with one of the contactors oi saidset, said periphery being recessed at different portions for enabling the contactors to open, a motor for driving said wheel continuously at a predetermined speed, and means also driven by said motor at a rotative speed different from that of the code Wheel for intermittently shorting said contactors thereby to render the operation of the code wheel ineffective.

2. A signature code transmitter having two pairs of make-and-break contacts, corresponding contacts of each pair being parallel-connected, a code signal cam for actuating a contact of the first pair, a cam for closing the contacts of the second pair during a relatively long time interval and for opening the last said contacts during a shorter time interval, and means for driving said cams continuously at different speeds such that different ones of a succession of different signatures are keyed by the code signal cam in cooperation with the contacts of the first pair during successive openings of the contacts of the second pair.

7 3. A device as defined by claim 2 and having said cams mounted for rotation on different shafts, one shaft being geared to the other in the ratio of three to seven.

4;. In a device of the class described, a code signal keying cam having raised and depressed portions of its periphery arranged in accordance with a plurality of different trains of code signals of station identifying significance, a keying circuit including a make-and-break contactor engageable with the raised portions of said cam, means including a second cam and a second contactor operable thereby for intermittently by-passing energy around the first mentioned contactor, means for rotating said cams continuously, and means including gears for maintaining a predetermined cycle of keying operations characterized by the keying of code signals of one train, as formed on one sector of the keying cam, then by continuous flow of energy through the second contactor while the keying cam makes an integral number of revolutions, then by the keying of code signals of a second train as formed on a second sector of the keying cam, then by a second period of energy flow through the second contactor as before, and so on until all of the sectors of said keying cam have been utilized to key their respective trains of signals.

5. In a high frequency carrier wave radio communications system having terminal transmitting and receiving stations, at least one intermediate relay station, and keying means for identifying by call code signals the different transmitting and relay stations, the method of transmitting code signatures Which comprises keying at the transmitting terminal all the signatures for the respective transmitting terminal and relay stations, causing each relay station to repeat the transmission of said signatures as modulations of a different carrier frequency, causing said signatures to be impressed upon the different carrier waves as keyed marking and spacing units of a predetermined tone frequency, and continuously modulating each of said carrier waves, as respectively radiated by the different stations,

by said tone frequency for predetermined time intervals between successive transmissions of one and the next signature.

6. The method as defined in claim 5, and including the process of utilizing the keyed signature tone modulation to start up each relay and receiving station and to maintain thesame receptive of trafiic signals originating at said terminal transmitting station, and. repeated by each repeating station.

'7. In a system for transmitting a remote control tone frequency from a sending to a receiving station and for intermittently keying said tone frequency by trains of code impulses having station-identifying significance, the method of spacing apart in point of time a plurality of different trains of said code impulses which comprises performing the keying function for the different trains consecutively and continuously, and by-passing the energy of said tone frequency during time intervals equal to a multiple of the time consumed in keying the impulses of a single station-identifying train.

WILLIAM KIMMICH.

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