US2142351A

US2142351A - Communication system

Info

Publication number: US2142351A
Application number: US38698A
Authority: US
Inventors: Clyde J Fitch
Original assignee: International Business Machines Corp
Current assignee: International Business Machines Corp
Priority date: 1935-08-31
Filing date: 1935-08-31
Publication date: 1939-01-03
Anticipated expiration: 1956-01-03

Description

Jan. 3, 1939. C. J. FITCH COMMUNICATION SYSTEM Filed Aug. 51, 1935 Patented Jan. 3, '1939 UNITED STATES PATENT OFFICE 2,142,351 COMMUNICATION sirs'rEM` Clyde J. Fitch, Endicott, N. Y., assigner to 1nternational Business Machines Corporation, New York, N. Y., a corporation of New York' Application August 31, 1935, Serial No. 38,698

1 Claim.

This invention relates to communication systems and more particularly to printing telegraph systems and is suitably adaptable to both radio and wire network transmission.

The present invention will be explained in conjunction with a single impulse synchronous transmission system, in which the different characters to be transmitted and received are repre- `by the transformation of the waveshape of the signal during the progress of its transmission or reception or both.

An object of this invention is to provide abbreviating means for controlling the time duration of the character pulse independently of the time duration of the impulse impressed on the input of the receiving system.

Another object of the present invention is to provide means for accomplishing the abbreviation of the signal impulses by utilizing a gaseous conduction device.

Various other objects and advantages of my invention will be obvious from the following particular description of one form of mechanism embodying the invention or from an inspection of the accompanying drawing; and the invention also constitutes certain new and novel featuresv of the construction and combination of parts hereinafter set forth and claimed.

In the drawing the circuits are shown which may be used in one preferred embodiment of the present invention.

It has been found that in synchronous systems of the type to be described, namely, the single impulse system, the margins of operation at higher rates of transmission become quite limited. For such rates of transmission, it is necessary to maintain exact synchroni'sm between the transmitting and receiving distributors, and in addition thereto, to transmit and receive the character signals by extremely short impulses, so as to be positioned or allocated properly on the distributor segments. However, it is well understood by those skilledv in the art, that transmission of signals either by radio or line networks under such critical conditions set forth numerous disadvantages, and prevent the higher rates of transmission of character signals without utilizing complicated and elaborate correcting systems, which for commercial application and operation would be impractical.

It has been suggested to utilize a longer impulse for transmission purposes, and which is necessary for radio transmission due to distortion and mutilation of the signal Wave Shapes, and upon its reception at the receiver, to suppress or abbreviate the signal so as to impress but a part of it upon the respective distributor segments.

A system of this type is' disclosed in a copending application, Serial No. 730,906, filed June 16, 1934, the principle of which appliedto the above mentioned system renders faster possible rates of transmission than heretofore. The system just mentioned in the said application is based on an electrical abbreviating system utilizing thermionic devices adapted to trigger controlling electrostatic devices.

The present invention contemplates a similar treatment of the signal Wave shapes, however, in

a more simple and cheaper manner, that is by utilizing gaseous conduction devices.

Inaccordance with the present invention a condenser having a slow charging rate, is em. ployed in connection with a gaseous conduction device having a denite breakdown potential, the condenserbeing bridged across the gaseous conduction device so that after a predetermined period of current flow the condenser accumulates a charge equal to the breakdown potential of the gaseousl conduction ltube and discharges therethrough, the discharge continuing until the charge is reduced to the lower limit of the operating voltage of the tube, at which time the discharge is discontinued abruptly.

It is the abbreviated impulse that is then applied or allocated on the commutator segments of the distributor so as to permit faster rates of operation of the distributor and hence a greater rate of transmission of intelligence.

It has mentioned hereinbefore that the particular type of communication system explained in conjunction with the present invention is a printing telegraph system operable by a line or radio network and involves the shifting of the character impulse along the axis of a timed scale, the position of the impulse thereon deter-f mining the character to be selected, and is of the type disclosed in U. S. Patent No. 1,927,077, dated September 19, 1933.

Referring now to the drawing A represents a printing telegraph unit which may comprise any well known typewriter having a series of character pivoted key bars I0 and adapted to initiate a character impulse when one of the character keys is depressed.

The transmitting contacts may be positioned and associated directly with the key bars as shown, wherein, a separate contact II is associated with each individual key bar I0 and connected to the segments I2 of the rotary distributor I3, a portion of the development of which is shown, and further disclosure thereof is deemed unnecessary since their use is well known in the art. Rotary arm Il driven by any vsuitable means, such as a motor, is adapted to engage the segments in rather rapid succession to cause the transmission of the character pulses.

One method of setting up the character signals is by the use of condensers and as shown an individual condenser I5 is associated with each key bar Il), the said condensers connected by a common conductor to one side of a battery It.

It is to be noted that all the contacts iI, that/ is the normally closed contacts, are associated with separate conducting segments I2 of the distributor I3.

Disposed beneath and associated with the key bars I0 'and normally open are the contacts I1 and connected to one side of the condensers I5. These are provided so that when a character key is depressed the associated condenser I5 normally charged will be discharged by shorting the condenser through contact Il to ground.

supposing the key bar corresponding to character A is depressed to discharge its corresponding condenser, upon return of the key bar the contact II is closed to connect the circuit from the battery I6 through condenser I5 and the closed contact II to its corresponding segment I2--I, so that when the rotary arm I4 with its conducting brush engages contact I, a circuit is completed through the solid conductor ring I8, y conductor I9 and the connected parallel circuit consisting of resistor 20 and the primary winding of transformer 2|.`

Therefore, it is seen that upon completion of the circuit just described, by the rotary arm I4 engaging the segment I2-I of the distributor' the corresponding condenser conditioned upon depression of the A character key by its discharge, is now charged through the parallel circuit arrangement 20 and 2| to energize the secondary winding of the transformer and its connected circuit which may be a` wire or radio transmission network, utilizing transmitting equipment well known in the art and need not be described herein in further detail. ,f-

The broad principle of operation of single impulse systems of the type referred to, which is obvious, depends upon the synchronous operation of the distributing or rotary units associated with the respective transmitting and receiving units. Such synchronizing units are old and well known to those skilled in the art, and therefore a detailed description of this unit is not necessary.

It is sufficient to mention that one type of synchronizing unit is such utilizing periodic synchronizing impulse as, for example, a synchronizlng-impulse for each revolutionv of the transmitting rotary distributor, and usually arranged so that if the rotary distributor at the receiver lags as compared to the rotation of the transmitting distributor, the receiving rotary brush, by virtue of such lagging, engages a contact segment to energize electroresponsive devices by the transmitted synchronizing impulse to cause the rotary arm at the receiver to be advanced to such an extent during its rotation so as to traverse the distributor segments in step with the transmitting distributor. If the receiving rotary arm is leading the transmitting, engagement of another contact segment causes the electro-responsive devices to retard the rotation of the rotary arm until synchronous operation is attained. For a complete description of a synchronizing unit of the type just mentioned, reference may be made to the co-pending application Serial No. 684,362, filed August 9, 1933.

A receiving distributor 25 similar to the transmitting distributor I3 has disposed thereon the same number of segments 26 which are engaged in succession by the brush attached to rotary arm 2l driven-by a suitable motor or device so that the arms lll and 21 are rotated synchronously.

The aperiodically timed character signals are received in the well known manner by a receiver, generally designated, to energize the type bar solenoids 28 which are connected independently to the contact segments 26 of the distributor. The circuit is completed by connecting the'common terminals of the solenoids to the solid conducting ring 29. i

Interposed between the signal receiver and the distributor and recorder is a circuit embodying a gaseous conduction device 30.

The gaseous conduction device 30 may consist of a pair of opposed closely spaced electrodes 3| and 32 contained within a sealed envelope filled with one of the monatomic gases such as neon, argon or helium or mixtures thereof, the pressure of the gas and spacing of the electrodes being such that the device will have a definite starting or breakdown potential.

It is a characteristic of negative glow tubes of this nature, when the electrodes are thoroughly degasied and cleaned and pure gas employed, to have an extremely uniform starting or breakdown potential over a long period of time, particularly when operated at .low current Adischarges, and after the discharge has been initiated therethrough, to continue to conduct current until the voltage has decreased considerably below the value required to start the'discharge.

The condenser 33 bridging the gaseous conduction device, gradually assimilates a charge over an interval of time depending upon the capacity of the. condenser and the value of the resistance 34, until it approaches the Value of the breakdown potential of the tube 30.

When an additional charge is impressed on the condenser 33 due to a received pulse impressed upon the circuit, the charge is such as to reach the breakdown potential of the tube 30. The condenser then discharges through the tube and energizes the primary winding of the transformers 35. The discharge continues until the voltage has decreased to the lower limit of the operatlng voltage of the tube and is then abruptly discontinued. The rate of discharge may be regulated by the value of the resistance 15a. In this manner the length of the impulses impressed on the contact segments 28 of the distributor can be controlled to conform to various rates of operation of the system. It is understoodthat the length of the impulses can be varied by altering the characteristics of the circuit and that this pulse impressed on the segments remains quite constant irrespective of the length of the impulses impressed on the signal receiver.

In order to operate the described `system at 1| greater rates of speed, an abbreviator method of the type `disclosed comprising the gaseous conduction device and associated elements is highly desirable due to its simplicity and eectiveness in increasing the operating margins of the system.

While there has been shown and described and pointed out the fundamental novel features of the invention as applied to a single modication, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art without departing from the spirit of the invention. It is the intention therefore to' be limited only as indicatedby the scope of the following claim.

What is claimed is:

A printing telegraph system comprising, in combination, means to receive periodic character signals, a printing telegraph recording unit, a signal control circuit connected to said receiving means including serially a gaseous space discharge device, a first and second resistance and a source of voltage, said source of voltage being below the break-down voltage of said device, a condenser connected in shunt of said discharge device andthe rst said resistance and also in shunt of the source of voltage and the second resistance, said condenser arranged to be charged relatively slowly through the said second resistance when character signals are not impressed on said' circuit, and outlet circuit to said recording unit connected across said first resistance so that upon reception of the character signals the said outlet circuit is energized by the discharge of said device and condenser and the rst said resistance controls the duration of the character signals sent over said outlet circuit, said outlet circuit inductively coupled to the receiving means in order that said signals may control the operation of the recording unit.

CLYDE J. FITCH.

CII