SU333888A1 - DECODER - Google Patents

Description

The invention relates to television technology and is intended for use in receivers of a color television system such as SECAM.

The decoders of the receiver of a color television system of the LhKAM type are known, in which the direct or delayed channels are connected to a vertical scanning unit, which increases the noise immunity of the color lock system by extracting an identification signal with a frequency of 7.5 kHz.

However, B of the known devices uses only half of the identification lines.

In order to increase the noise immunity of color synchronization in the proposed device, a signal from the vertical scanning unit of one electrical circuit is supplied to the electronic switch.

FIG. 1 is given a block diagram of the proposed device; in fig. 2 shows an embodiment of an electronic switch; in fig. 3 shows an example of execution of the identification block; on fit. 4 is another exemplary embodiment of the identification block.

The decoding device contains a bandpass amplifier 1, to the input 2 of which a chrominance signal is fed, direct and delayed channels 3 and 4 connected via an electronic switch 5 to color difference channels 6 and 7, whose color difference video signals are output at outputs 5 and 9. The electronic switch 5 is controlled by a signal from a relaxation generator 10, which

it is excited by pulses from a horizontal scanning unit applied to the input //. In addition, the device contains an identification unit 2, one or two signal inputs (13 and 14) of which are connected to the outputs of color different channels. The control input 15 of the identification unit is connected to the vertical scanning unit 16. The identification unit has two outputs: the output 17 of the phase correction is connected to the input 18 of the correction of the relaxation generator;

shutdown output 19 is connected to input 20 or control input 21 on and off of a decoder. The inputs of the electronic switchboard are also provided with signals from the personnel development unit.

The proposed device works as follows.

For the time of the frame extinguishing interval, the impulse from the frame scanning unit switches the switch to such a position

when the signals arriving at the input of the switch pass to the output b, and the signals arriving at the input b pass to the output r, i.e., for the time of the frame blanking interval, the switch ceases to be controlled

output b is direct signals, and output g is delayed. The mode of operation of the switch corresponds to a variant of the proposed decoding device, in which there are two connections between the switch and the delay unit.

In the variant with one link, the output of b during the extinguishing frame interval receives only a direct signal, in which the components D and D are alternated from line to line; At the same time, the switch branches that are suitable for the output of g continue to function normally, and the output of the switch r is alternately transmitted either directly or delayedly, containing only the components of Dv.

The dots 22 and 23 of the four-diode switch (Fig. 2) are connected to two opposite-polar outputs of the frame scanning unit. During the return stroke, the negative pulse is transmitted to point 22, and the positive polarity is sent to point 23, while diodes 24 and 25 are unlocked, and diodes 26 and 27 are locked. As a result, a non-switched direct signal arrives at the input of one color-difference channel during the period of a frame extinguishing interval, and a non-switched delayed signal arrives at the input of another channel.

In the second version of the device, the frame is connected to the frame one block; only one point 22 of the switch is connected, the switched chroma signal is output at one switch output, and the non-switched signal is allocated at the other output of the switch frame.

The two proposed options for a decoder (ic two and with one connection of a switch with a frame scanner unit) allow the identification unit to be built in different ways, depending on what specific requirements are placed on the parameters of the receiver or decoder.

As an example, two schemes of the identification block from a greater number of possible are considered.

The first example is explained in FIG. 3 and relates to a variant of a decoding device in which there is one connection between a switch and a vertical scanning unit. The signal outputs of the identification unit are connected to the keys 28 and 29, the control inputs and the signal from the vertical scanning unit.

The output of the key 28 through the filter 30, which is tuned to a frequency of 7.5 kHz, is connected to the output of the phase correction.

The output of the key 29 through the integrating circuit 31 is connected to the first input of the chroma switch 32, the second input of which is connected to the vertical scanning unit, and the output to the first input of the 33 “OR cell, to the second input of which the signal from the vertical scanning unit is fed.

Consider the second exemplary embodiment of the identification block according to the present invention. The scheml contains one key 34, controlled by a vertical scanning unit (Fig. 4). The bi-polar identification signal, taken from the key output, goes directly to the phase correction output. Same signal

through valve 35 is applied to the color switch 36. The decoding device is turned off for the active time of the field if a color program is received, regardless of whether the phase has been corrected or not.

Subject invention

A color television SECAM receiver decoding device containing a bipolar electronic switch, to one input of which the chrominance signal goes directly, and to the other through a delay line for the time of one line, a relaxation generator controlling

the switch and connected to the line scanner, two color difference channels, the inputs of which are connected to the outputs of the switch and the identification unit, the signal input (or inputs) of which are connected to the output

(or outputs) of the color difference channels, the control input is connected to the vertical scanning unit, the phase correction output is connected to the relaxation generator, and the off output is connected to the input (or inputs)

control off the decoder, characterized in that, in order to increase the color burst immunity, the electronic switch is connected to the vertical scanning unit, at least

least one electrical circuit.

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