US2168251A - Synchronizing system - Google Patents

Description

Patented Aug. l, 1939 SYN CHRONIZING SYSTEM Rudolf Urtel, Berlin, Germany, assignor to Telei'nnken Gesellschaft fiir Drahtlose Telegraphic m. b. H., Berlin, Germany, a'corporation of Germany Application May 20, 1936, Serial No. 80,692 In -Germany May 15, 1935 3 Claims. (01. 178-695) The present invention relates to a synchronizing system, and is more specifically directed toward synchronizing systems adapted for television 'and facsimile systems.

distinguishing characteristic of being of unequal the shorter synchronizing impulses duration; serving to synchronize the line formation while the longer impulses were utilized to synchronize for frame. Thus, for example, the line synchronizing pulses might have a durationequalto 10% of the time it takes to scan one line, while the frame synchronizing impulse might be equal to 10% of the time to scan one picture frame. Separation at the receiver of these synchronizing signals was accomplished by amplitude separor frame synchronizing impulses is accomplished by frequency selection in the following fashion:

The synchronizing signals are fed to a parallelly connected condenser and resistance of such time constant that the line synchronizing impulses of brief duration are unable'to change the potential across the network appreciably, while the frame impulse of long duration is ableto produce a large change in potential across the network. The change in-potential is used to control thermionic tubes to produce synchronization. The result, however, of such frequency selection is that the beginning of the frame impulse, instead of being sharp is distorted. That is to say, the build-up time being appreciable changes the sharp slope of the framing impulse into one of relatively small slope. This causes blurring and imperfect and faulty synchroniza-. tion. While this defect is not of such great importance in the usual standard method of scanning in which lines of one frame coincide or are in register with lines of preceding frame, the error becomes very important when interlaced scanning is used.

It is accordingly, one of the objects of my in- For example, the amplitudes might be way be used in other fields. The picture impulse vention to provide an improved synchronizing method for television and facsimile systems.

It is a further object of my invention to eliminate blurring of images due to faulty synchronizing produced bynetwork distortions. l B

A further object of my invention is to provid means to correct for distortion in synchronizing signals.

A still further object of myinvention is to provide a synchronizing method which will enhance the operation of television and synchronizing systems utilizing interlaced scanning,

Other objects and advantages of my invention will be readily apparent to those skilled in the art upon reading the following description of 15 my invention taken in conjunction with the draw ing.

Referring now to the drawing:

Figs. 1a and 1b are representative of interlaced scanning patterns; 20 Figs. 2a, 2b, 2c, 2d, 2e, and 2! are representa-' tive of the types of synchronizing signals received after being distorted and finally reshaped by applicants invention; and

Fig. 3 shows one embodiment of applicants invention for overcoming distortion in' the synchronizing signals.

Where interlaced scanning is used, the lines I of one picture must fit exactly on the gap ofthe preceding picture, as shown in Fig. la. Slight deviations make the pairing of the lines apparent and this means a coarse structure of the image,

as clearly illustrated in Fig.1!) where a departure of only 10 percent has been assumedfor the line interval. By such line pairing in the scan- 35 ning of the picture there results a picture scan equal to one-half the normal number of lines.

Accord ng to this invention a better time-definition of the picture is to be obtained in television. The invention, of course, may in a similar is so made that it is resolved into a preparatory or announcement order and an execution order. During the re-creation of the picture, the frame synchronizing device is entirely blocked sothat the impulses cannot affect the picture reproduction. Frequency selection, which, as

above pointed out, entails impulse blurring or 'formance impulse which is not routed through a filter causes the actual change of picture so that. there will be a sharply defined initiation and beginning. 55

not cause any noticeable voltage variation across the suitably chosen parallelly connected resistance and capacity network are followed by the .tive pole of a voltage supply I.

picture impulse which is badly mutilated at the point marked 1'. Asa consequence, the time definition of the picture change is extremely faulty. In a similar way, Figs. 2c and 2d illustrate the distortion occurring in another type of signalling where a long impulse is transmitted instead of a long spacing period.

Using the same mode of illustration as in Figs. 2a2d, Figs. 2e and 2 illustrate the structure of the picture synchronizing impulse consisting of the announcement or preparatory signal a and the execution signal b.

A circuit organization adapted to carry the basic idea of the invention into practice is illustrated in Fig. 3. In this figure a thermionic discharge tube I, having a control electrode, plate and cathode, has its plate connected to the posi- Connected in series with the negative pole of the voltage supply and the cathode of tube I is a filter comprising a resistance 3 and a condenser 5. Input terminnals l5 are connected to the control electrode of tube I and to the cathode of the tube. A gaseous discharge tube 11 has its cathode connected to the cathode of tube 1. The control electrode of tube 11 is connected through a condenser H to the control electrode of tube I. The anode of the tube II is connected to one side of the load circuit, while a voltage supply 8 has its positive pole connected to the other side of the load, while vits negative pole is connected back to the common cathode connection. A serially connected resistance and biasing source Eg is connected to the control electrode of the tube II and to the junction point of the negative pole of the voltage source I and the filter comprising the resistance 3 and condenser 5, so that the tube II is negatively biased, and being of the gaseous discharge type, is normally in such a condition that no current flows through the plate circuit of the tube and the load L. It will thus be evident that the control electrode of the tube II has its control electrode potential determined by the value of the biased battery Eg and' the. potential drop across the filter comprising the resistance 3 and the condenser 5. The potential across the filter the terminals IS. The impulses are fed to tube I. Across the resistance of filter 3--5 -is caused to arise a potential which so biases the grid of the gaseous discharge tube 11 that the impulses will leave tube II unaffected. Lacking line impulses (announcement or preparatory signals) permit the potential at the filter 3-5 to decay so that, while auxiliary voltage E; may still block the gaseousdischarge tube 11, the unfiltered and therefore steep execution impulse will be caused to result in the steep wave fronts. The discharged energy is then utilized in the load circuit L to synchronize the system in any of the manners well known to the art.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In a television system, the method of synchronizing a television receiver which includes the steps of receiving line synchronizing signals of predetermined time duration transmitted sequentially with frame synchronizing signals having a time duration greater than'that of the said between said line signals and large compared with the duration of the said frame signal, preparing for the generation of a synchronizing impulse during the duration 'of the space between said line and frame signals, and initiating the generation of the said impulse with the commencement of the frame synchronizing signal.

2. A synchronizing system for a television receiver comprising means for. receiving line synchronizing signals of predetermined time duration transmitted sequentially with frame synchronizing signals having a time duration greater than those of said line signals and spaced from said line signals by a time interval greater than the time interval between successive line signals'and greater than the time duration of said frame signals, means for preparing for the generation-of a synchronizing impulse during the duration of the space between said line and frame signals, and means for initiating the generation of the said impulse with the commencement of the means for transmitting a portion of the receivedsignals through a network including a filter to produce a filtered frame signal, means including the filtered frame signal for preparing for the generation of a synchronizing impulse, and means for initiating the generation of the synchronizing impulse by an unfiltered portion of the received signals.

RUDOLF URTEL.

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