US2055985A - Idle time keying apparatus - Google Patents

Description

Sept. 29, 1936. H. o. PETERSON IDLE TIME KEYING APPARATUS 2 Sheets-Sheet 1 Filed Dec. 23, 1933 12 .1

70 HAD/0 T/M/VSM/TTKR INVENTOR H .0. PETERSON w z OWER .S'UPPZY ATTORNEY- Sept. 29, 1936. H Q PETERSQN 2,055,985

IDLE TIME KEYING APPARATUS Filed Dec. 23, 1933 2 Sheets-Sheet 2 4/ auro/e POM 5f? JUPPZ Y ncccYooooooooao/ INVENTOR H.( )..P T SON BY AT TO RN EY Patented Sept. 29, 1936 PATENT OFFICE mm 'rmn KEYING APPARATUS Harold Olaf Peterson, Biverhead, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application December 23, 1933, Serial No. 703,783

This invention relates to idle time keying circuits for use with printing telegraph apparatus on radio circuits.

In communication by radio it is frequently necessary, in order to maintain circuit contact,

for the attendant at the receiving station to check the tuning adjustment of the receiver with the transmitter. When message signals are being sent over the radio channel it is the practice to utilize these same signals for the supervision of the circuit, but during idle periods it is customary to transmit frequent test signals to maintain a continuous assurance that the overall circult is functioning; otherwise, some adjustment of either the transmitter or receiver might change during the idle period, a condition which might consequently result in no response at the receiver when the transmitter resumes operation.

cedure, howeverg has not proven convenient on printer circuits; consequently, it' has been the practice to use reversed keying. In this type of operation the marking impulses appear as-spaces on the transmitted signal. Thus, a steady dash will be sent during the intervals between transmissions. While the radiation of steady dash between transmissions proves to a very effective way of maintaining circuit contact, it has been found to constitute a continuous dissipation -of power and wear and tear on the transmitter tubes.

It is the primary object of the present inven- According to the present invention it is proposed to transmit letters from the printer equipment at even intervals at a. ate of approximately 24 letters per minute, a number which it is found maintains satisfactory contact over the circuit. The keying is arranged so that the transmitter radiates energy only during the marking impulses from the printer. Since the full speed transmission rate for a typical printer is 3'72 letters per minute, and since each letter does not constitute marking impulse, it will be seen that a-considerab1e saving of power and tube life maybe obtained by the use of a device for sending a reduced number of letters, let us say, ap-

proximately 24 spaced letters per minute. The number of these spaced letters per minute may,

4' Claims. (CL 178-79) of course, be varied to suit circuit conditions and in some cases the number may be considerably reduced.

The invention is accomplished, in accordance with one embodiment, by the provision of auto-' matic contactor apparatus for causing the transmission of the test letters, this apparatus being attached directly to the keyboard for movement of a particular letter key, while, in another embodiment, apparatus is connected to the mechanical or the electromechanical parts of the printer itself whereby the desired letters are transmitted by the automatic operation of the clutch lever or the trip oif pawl of the mechanism. In a third embodiment, the transmitter message channel is connected to switching mechanism which may then associate the channel either with theaprinter or with a generator of impulses, this generator being any suitable device, such as a commutator rotating at a desired velocity and having segments of desired length. Other embodiments'will. readily suggest themselves from a reading of the specification.

One feature of the invention is an indicator arrangement in the form of a photoelectric scanning device at the receiver for actuating an alarm whenever there are received letters other than the predetermined test letter.

The invention is described in more detail in the accompanying specification which is accompanied by drawings wherein Figures 1, 2, 3, 3a and 4 schematically illustrate different embodiments of the invention, and Figure 5 shows an alarm device at the receiver for attracting the attention of the attendant whenever the test letter is not correctly received.

Referring to Figure '1, there is shown a standard printer I in circuit with a line 2 extending to a radio transmitter 3 arranged to radiate energy over an antenn 4. Fixedly attached to the printer by means of a suitable bracket frame support 5. is a plunger device 6 which'acts on any desired letter key. This plunger is operated upon by a cam 1 which is located on a shaft 8 geared through reduction gears 9 to a motor l0, current for which is supplied over leads II. The end of the plunger is covered with a soft mate ial, such as rubber, and its position is adjusted o as to depress the key a desired amount. A spring I! serves to return the plunger to normal.

In the operation of the device during idle time intervals, rotating cam 1 functions to periodically cause the plunger to depress the desired key line 2 to the distant radio transmitter from which the signals are sent out'to the antenna 4.

Figure 2 shows another embodiment wherein a plunger I3 is actuated against the pull of a spring H by the operation of an electromagnet l5 whose armature l6 rests against the upper portion of the plunger. Spring l4 serves to return the plunger to its normal position. A contacting device I! located on shaft 8 and comprising an insulating disc having on its periphery a metallic segment 20 and connected thereto a metallic ring 22 acts periodically to close a circuit which may be traced from one side of battery l8, brush l9 and segment 20, connecting lead 2|, ring 22 and brush 23, through the winding of magnet l5 back to the other side of battery l8. The closure of this circuit, which occurs whenever segment 20 makes contact with brush is, causes the operation of magnet l5 with the consequent depression of plunger I3 upon the selected key of the printer I. It will be noted that contacting device H may be operated in other ways than by the motor indicated, as, for example, by a thermostatic operated make and break contactor of the make and break type such as commonly used in blinker light circuits.

In Figure 3 is shown another embodiment wherein, instead of making use of the regular mechanism of the printer, there is provided a rotating commutator 24 having a conducting ring 25 connected to segments 26, which are of proper length to give a normal test signal during idle periods, for operation of the receiving printer at the other end of the circuit. In this case, it is necessary to control accurately the velocity of the commutator, and this is accomplished by the provision of a governor 21 or by making motor I 0 a synchronous motor operating on suitably regulated alternating current. A double throw, double pole switch 40 serves to connect the radio transmitter with either the printer or the idle time test character commutator, as desired.

In the drawings, the segments 26 are shown; occupying a small percentage of the total comf mutator. If desired, these segments may. e

spread out over a large portion of the circpmference and made to operate the outgoingcontrol circuit through this character forming commutator in series with another commutator operating at very slow speed and bearing a contact segment covering a small portion of its total circumference. This second contact wheel would be geared to the same shaft as that driving the character forming commutator through a reducing gear of suchyalue that the circuit to the transmitter is established only once during a predetermined number of revolutions of the contact forming commutator. Thus, it is possible to send the test letter at proper speed to operate a receiving printer, but at spaced intervals on the order of approximately two seconds between each transmission of the test signal. Such an arrangement is shown in Figure 3a. where the length of the segment 4| on the second contact wheel 42 corresponds to one full revolution of contact wheel 24. The operation of the circuit, it is thought, will be obvious from a mere inspection of the drawings. It will be appreciated that this character forming commutator might be driven by means other than a rotating motor.

Figure 4 illustrates a still further modification wherein the idle timekeying device operates on the mechanical parts of the well known Kleinschmidt printer. Since the printer itself forms no part of the invention per se, only that portion of the printer.is shown which is necessary for a proper understanding of the invention. The drawings show in part a vertical cross section of the printer wherein an electromagnet 28 acts to pull forward the trip off pawl 29 whereupon the printer transmits the test character as determined by the setup of the selector bars which remain in the position determined by the last letter sent out by the printer by the operation of the printer keys in the normal manner. The electromagnet 28 is controlled by means of a commutator driven by a motor, as shown.

In Figure 5 is shown a photoelectric scanning device for automatically actuating an alarm upon the incorrect receipt of test letters. Assuming in this case, that the test character is the punctuation mark period, the photocell-will receive sufficient light reflected by a strip of tape 30 (bearing a string of black dots representing periods) from a source of light 3| to cause the operation of a relay 32 in the anode circuit of an amplifier 33.

When other characters such as letters appear on 0 the tape, less light will be reflected, upon the occurrence of which the anode current in the amplifier will be reduced and relay 32 will fall back to close a circuit operating the alarm 34.

The embodiments of the invention illustrated and described herein have been selected for the purpose of clearly setting forth the principles involved. It will be apparent, however, that the invention is susceptible of being modified to meet different conditions encountered in its use, and it is, therefore, aimed to cover by the appended claims all modifications within the spirit and scope of the invention.

I claim:

1. In combination, a transmitting printer having a keyboard, a plunger associated with a key of said keyboard, an electromagnet for actuating said key, and a revolving circuit closing contact device for periodically operating said electromagnet.

2. In combination, a transmitting printer having a keyboard, a support carried by said keyboard, a plunger mounted for reciprocation in said support, said plunger bearing on a key of said keyboard, and means for periodically depressing said plunger and consequently manipulating said key of said printer for the transmission of test characters from said printer.

3. In combination, a transmission line, a transmitting printer connected to said line said printer having a keyboard, a support on said printer, a plunger mounted in said support and associated with a key of said keyboard, an electro-magnet and a lever arrangement cooperating with said plunger for actuating said plunger to depress said key, and means for periodically operating said electro-magnet.

4. In combination, a transmitting printer having a keyboard, a plunger supported by said printer and cooperating with a key of said keyboard for periodically depressing said key of said keyboard, means for operating said plunger, the frequency of operation of said plunger being under control of a motor connected with said operating means, and gear reduction means between the shaft of said motor and said operating means for controlling the operation of said plunger.

HAROLD OLAF PETERSON.

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