DE1282682B - Circuit arrangement in a multi-standard television receiver with selection and switching when receiving television programs with different line standards - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

H04n

German class: 21 al -35/10

Number: 1 282 682

File number: P 12 82 682.3-31 (C 39885)

Filing date: August 16, 1966

Opening day: November 14, 1968

The invention relates to a circuit arrangement in a multi-standard television receiver with a line standard selection and switching device for setting the receiver when receiving television programs with different norms to the desired line norm, whereby for norm switching the output signal of the line norm selection device is used.

Such circuit arrangements for automatically switching the line standard to multi-standard receivers are already known, for example from the German Auslegeschriften 1179 585 and 1194 897. These known arrangements work with a switching relay, which is from an oscillating circuit system is controlled. The use of resonant circuit systems to control the line standard switching has the consequence, however, that in the case of noisy signals, there is a low level of reliability is present. To reduce this difficulty, either two very selective oscillating circuits are required (German Auslegeschrift 1179 585) or a special transformation for the necessary reverse voltage a switching tube (German interpretation 1194 897).

A television receiver for receiving broadcasts according to various television standards is still known from the German Auslegeschrift 1153 061. It is used as a switch for processing differently designed picture change pulse sequences of different television standards an actuating device provided, depending on the respective number and / or shape of the image change pulses controlled by an amplitude filter for synchronizing an image deflection oscillator will. A clear switchover of the line frequency takes place here only when the switch one of a further switching criterion, e.g. B. the line frequency, dependent actuator has, which requires an increased circuit complexity.

The invention is based on the object of a simple and fail-safe automatic Line norm selection and switching when receiving television programs with different To create line norms. To solve this problem, in a circuit arrangement, the initially mentioned type proposed according to the invention that the line standard selection device from a gate having several inputs, the line frequency at one input the signal representing the received television program and the line frequency at another input receives the signal representing the receiver,

Circuit arrangement in one
Multi-standard television receiver with selection and
Switching when receiving
Television programs with different
Line norms

Applicant:

Communications Patents Ltd., London

Representative:

Dipl.-Ing. R. Minetti, patent attorney,

2000 Hamburg 1, Ballindamm 15

Named as inventor:

■ ^! Gunärs Berzins, Frimley, Hampshire;
^ao Eric John Gargini,

West Dryton, Middlesex (Great Britain)

Claimed priority:
_a5 Great Britain from August 18, 1965 (35 429) -

and that if the gate input signals match, there is no output signal of the gate.

An essential advantage of the invention is that in the event of an unsuccessful line standard selection the switching process is repeated until the correct line standard is set. To this Way, high reliability of the automatic switchover is guaranteed.

The invention is particularly directed to a television receiver that can receive television programs from two different line norms can receive. The selection device for setting the Receiver designed to receive television programs of the desired standard so that at Actuation of the selection device of the receiver in the state of receiving programs of the other line standard than the one to which the line standard selection device was set before this time was set in response to an output of the gate. In this case the gate is with two Provided inputs, one of which is separated from the synchronization pulses and the second from the Line oscillator stage of the receiver receives derived pulses. If the two input pulses in

809 637/801

occur essentially at the same time, the output of the gate should be signal-free.

The gate circuit can preferably be a multi-grid electron tube, z. B. in the form of a pentode, the control grid of which the separated synchronization pulses and whose catch grids receive the pulses derived from the line oscillator stage.

The invention is explained in more detail below using an exemplary embodiment, specifically in * ° Connection with the drawing showing a circuit diagram of part of a television receiver according to the invention shows.

The television receiver to which the embodiment relates is intended to operate at the S ¹ 405-line system with positive modulation, and in the 625-line system with negative modulation. In such a receiver, the synchronization pulses appearing at the anode of the synchronization separation circuit are negative when the receiver is set to work with the same line standard as the television signals to be received, while the corresponding pulses when receiving signals from the program of the other line standard become positive. These signals appearing at the anode of the synchronizing separation circuit are fed to a gate formed by the pentode Vl with two inputs at A as the first input. This input fed according to the drawing the control grid of the tube Vl through a limiting resistor R 1 3 »and a coupling capacitor C 1. The resistor R2 serves as Gitterableitwiderstand.

The second input of the gate pulses are derived from the line oscillator of the receiver, applied at B to the catching grid of the tube Vl. These pulses reach the braking grid via a limiting resistor R 3 and a blocking capacitor C 2. The resistor 2? 4 is again a grid leakage resistor, while the capacitor C 3 is used to ensure phase equality between the pulses on the braking grid and the pulses occurring on the control grid. The diode D1 is provided to clamp the potential to ground.

The screen grid of the tube V1 is connected to a voltage source of high potential, as indicated schematically. The output signal of the gate formed by the tube Vl takes the form of an anode current pulse train. The anode current leading to the tube flows through a relay RY, so that the relay RY is temporarily excited when the anode current pulses 5 <> occur. A pair of contacts RYl of this relay is to control the switching for the line standard in a suitable manner so that the receiver is placed in the state of receiving television signals of the other line standard than the standard received at the moment.

If, for whatever reason, the line frequency of the receiver does not trigger synchronization when the relay RY is switched to the correct standard, the relay can be actuated repeatedly. This causes the recipient to switch from one line standard to the other until synchronization finally occurs. To avoid in these circumstances, an unnecessary repetition of the switching process, is connected to the relay RY, a resistor R 5 and capacitor C 4 containing .RC circuit that limits the number of successive actuations of the relay RY. The time constant of the element RSIC 4 is advantageously dimensioned so that only two successive switching operations are possible.

In order to keep the risk of failure of the line pulses of the receiver for synchronization as small as possible, a second contact pair RY2 can be combined with the relay RY in a receiver with a flywheel synchronization circuit, which is used to temporarily expand the pull-in range. This extension of the drag range can be brought about, for example, by shortening the time constant in the usual feedback loop of the flywheel synchronization circuit.

In some cases it may be desirable to apply low amplitude line flyback pulses to the control grid of the tube Vl at a level sufficient to ensure that the tube is normally in the "cut-off" state. At C, these pulses can be fed to the control grid via the resistor!? 6 from the line deflection stage.

It can be seen that, due to the present invention, a television receiver with relatively little expensive additional means can be designed so that its line deflection circuit is reliably set to the line frequency standard of the television programs to be received.

Claims (5)

Patent claims: 1. Circuit arrangement in a multi-standard television receiver with a line standard selection and switching device for setting the receiver when receiving television programs with different norms to the desired line number, whereby for norm switching the output signal of the line norm selection device is used, thereby characterized in that the line standard selection device consists of a plurality of inputs having a gate, the line frequency of the received at one input The signal representing the television program and the line frequency at another input of the receiver receives the representative signal, and that if the gate input signals match there is no output signal from the gate. 2. Circuit arrangement according to claim 1, characterized in that the gate is a multi-grid tube, z. B. in the form of a pentode (Fl) whose control grid contains the separated synchromeshing pulses and whose capture grid receives the pulses derived from the line oscillator stage. 3. Circuit arrangement according to claim 2, characterized in that an electromagnetic relay (RY) controlled by anode current changes in the tube (F1) is provided and its electrical contacts (RYl) are provided for controlling the line standard switching. 4. Circuit arrangement according to claim 3, characterized in that the electromagnetic relay (RY) has additional electrical contacts (RY2) for expanding the pull-in range of a flywheel synchronization circuit. which is connected to the line oscillator circuit of the receiver. 5. Circuit arrangement according to claim 4, characterized in that to comply with the Switch-off condition pulses derived from the line deflection circuit and the control grid in addition to be fed to the separated pulses. Synchronization Considered publications: German Auslegeschriften No. 1153 061, 1179585.1194 897. 1 sheet of drawings 809 637/801 11.68 © Bundesdruckerei Berlin