SU437247A1 - Device for extracting a line from a television signal - Google Patents

Description

one

The device relates to a television measuring technique, in particular to television oscilloscopes.

Devices are known for extracting a line from a television signal.

However, known devices have insufficient stability of line selection.

For normal operation of the device, the duration of the strobe pulse must be less than the length of a single line, then there may be a situation where the strobe pulse will appear between the horizontal sync pulses, as a result of which there will be no trigger pulse at the device output.

If noise is detected in the signal under study, it is possible for the device to re-activate within the line under study due to the passage of noise through the coincidence circuit during the gate-impulse action.

The aim of the invention is to increase the stability of line selection.

For this, the output of the frame delay pulse field is connected to the selector pulse delay circuit via a serially connected trigger, the output of which is connected to the second input of the coincidence circuit, a blocking pulse generator connected by an input to the output of the coincidence circuit, and the output of the blocking pulses is also connected to the second input trigger

The drawing shows a block diagram of the device.

A device for extracting a line from a television signal comprises a clock selector 1, a field selection circuit 2, a delay circuit 3, a trigger 4, a coincidence circuit 5, a blocking pulse generator 6, a selector pulse delay circuit 7. The device works in the following way.

The video signal is fed to the input of the sync pulse selector 1, from the outputs of which the field frequency pulses and the horizontal sync pulses arrive at the start of the field selection circuit 2. At the output of the field selection circuit 2, field pulses are generated corresponding to the frame sync pulses of either the first or second field. The pulses of the field trigger the delay circuit of 3 pulses of the field. By adjusting the delay of this circuit her

the output pulse is phased within the decomposition field. The delayed pulse from the output of the delay circuit 3 is fed to the first input of the trigger 4 with a separate start and overturns it. Output

the trigger, the voltage drop is fed to the input of the coincidence circuit 5 and permits the passage to the output of the horizontal sync pulses fed to its second input from the output of the clock selector 1. The first

line sync pulse

match 5, goes to lockout pulse generator 6 and starts it. The pulse from the output of the blocking generator 6 goes to the second input of the trigger 4 and, with its falling edge, tilts it back to its original state, preventing the 5 following horizontal sync pulses and noise pulses from passing to the output of the matching circuit. The duration of the blocking pulse is chosen so as to ensure the passage of a horizontal sync pulse through the scheme, i.e., in the order of several microseconds.

The leading edge of the blocking pulse triggers the selector pulse delay circuit 7, from the output of which a delayed pulse, phased by changing the delay within one to one and a half lines, goes to the output of the device.

By selecting the required decomposition floor using the floor selection scheme 2 and adjusting the delay of schemes 3 and 7, you can select the video signal at any point in the TV frame.

Due to the galvanic connection between the output of trigger 4 and the coincidence circuit 5, the installation of trigger 4 into the required initial

The state occurs automatically when the PA input signal is supplied to the device.

Subject invention

A device for extracting a line from a television signal, containing a clock selector, with a video signal input, the first output of the clock selector simultaneously connected to the first inputs of the matching circuit and the frame field selection circuit, and the second output through the frame selection circuit with the selector delay circuit pulse field frame, selector pulse delay circuit, characterized in that, in order to increase the stability of the line selection, the output of the frame delay pulse field is connected to

a selector pulse delay circuit through a serially connected trigger, the output of which is connected to the second input of the coincidence circuit, and a blocking pulse generator connected by the input to the output

matching circuits, with the output of the blocking pulse generator also connected to the second trigger input.