DE1143851B - Method of switching from one television signal to another - Google Patents

Description

GERMAN

PATENT OFFICE

kl. 21a ¹ 35/30

INTERNATIONAL KL.

H04f; n

F;

REGISTRATION DATE: AUG U S T 16, 1961

NOTICE THE REGISTRATION ANDOUTPUTE EDITORIAL: 21. F E B R U AR 1963

The invention relates to a method for resynchronizing a local pulse center by a different television signal at practically the same synchronization frequency.

If during a television broadcast in the program of the local studio program parts of someone else Studios are to be faded in without interference, the local studio is shortly before the foreign fade in resynchronized to the beat of the foreign studio. The external display can then be trouble-free can be done with all common types of dissolves. The previous resynchronization is still carried out within the local program portion and must go on so smoothly that the viewer on Home recipients practically do not notice anything.

It is known that a trouble-free resynchronization is only possible if the switching of the Synchronization takes place at a point in time in which the external and local horizontal synchronization pulses match in their phase. The synchronization is switched over by hand operated switch prepared and prepared with the former operated switch and with the first subsequent one Coincidence of the horizontal sync pulses carried out electronically. at Small differences in the synchronization frequencies will result in a random coincidence of the horizontal synchronization pulses reached in a sufficiently short time. With practically the same synchronization frequencies, as it is, for. B. at Precision offset operation can be done with a random coincidence of the horizontal sync pulses cannot be expected within the foreseeable future, and means must be provided which the phase of the local horizontal sync pulse in such a way influence that a coincidence is forced in a short time.

According to one known method, two mother generators are used to operate a local pulse generator provided, of which the first is synchronized by the sync pulses from an external pulse generator and the second mother generator initially controls the local pulse generator. This second mother generator can be detuned by about 1 Hz, based on the vertical frequency. If now the vertical impulses of the external impulse generator and the local impulse generator coincide in time, then automatically made such a switch that the local pulse generator now is controlled by the first mother generator. In this known method, a defined Frequency change made to the mother generator frequency so that the coincidence is not random Method of switching from one television signal to another

Applicant:

TV G.m.b.H., Darmstadt, Am Alten Bahnhof 6

Dipl.-Ing. Ernst Legier, Darmstadt, has been named as the inventor

he follows. However, this known method would not be applicable to a modern precision offset company, because a quartz generator is used as the mother generator, the frequency of which is within very narrow limits must remain constant and must not be changed under any circumstances.

According to a proposed method of switching from one remote signal to another is the phase of the horizontal sync pulses generated by the local pulse generator by means of a phase shifter shifted automatically depending on the phase difference of the horizontal sync pulses, and if the horizontal sync pulses coincide in time, the switchover is automatic made by means of an electronic switch. The invention represents a further development of this proposed procedure.

According to the invention, the phase is derived from the mother generator of the local pulse generator Horizontal sync pulses at the initiation of each switching process once over a range of at least one period and independent of the instantaneous phase position of the external horizontal sync pulses shifted with the help of a phase shifter, and at the moment of the temporal correspondence the actual switchover takes place with the external and local horizontal sync pulses in a manner known per se by means of an electronic switch. The method according to the invention draws are characterized in that the circuit arrangement for its implementation requires little effort Requires components and still enables a very reliable switching of the television signals.

It is useful if the horizontal sync pulses of the local mother generator are an electrical

309 510/183

3 4

tronic phase shifter, which then controls the local television studio when a sequence of horizontal sync pulses is initiated synchronously with each switching process. In this case, a signal is received that triggers the displacement of the local horizontal-horizontal synchronizing pulses generated in the local pulse generator 1 by at least one synchronizing pulse via terminal 17 of the sawtooth period. This control signal is to be fed to a bell generator 18, in which a horizontal potential curve is present, and this potential-frequency sequence of sawtooth pulses is generated and the tial change is to run so slowly that the frequency that is temporarily generated during this process is then fed to the phase discriminator 3. In the local pulse generator, there are also deviations compared to the horizontal synchronous vertical synchronous pulses or blanking pulses or frequency is relatively small. This frequency deviation io generates a synchronous mixture and should generally be less than V _{1000 of} the horizontal or 20 or 21 output via the terminals 19.

be synchronous frequency. To force the coincidence of the horizontal

In the following, the invention and synchronizing pulses are applied to the phase shifter 13

Execution examples of the same with reference to FIGS. 1 to 4 bell-shaped signal e of the shock function generator 22 described, with 15 shown in several figures supplied, which arises and disappears again with each actuation of the synchronous circuit elements or pulse sequences with sierumschalters 15.

the same reference numerals are identified. It shows such a signal can easily pass through Fig. 1 is a schematically illustrated circuit multiple integration of a square pulse generated arrangement to achieve the phase match. The signal is changed by switching a

the horizontal sync frequencies, triggered 20 switch 23, its coupling with the

FIG. 2 shows a more detailed illustration of the shock synchronous changeover switch 15 by the dashed line 24

function generator and the phase shifter according to Fig. 1, is indicated symbolically. In the drawn in Fig. 3 and 4 pulse sequences, denoted by a, b, c, d, switching position of these switches 15 and 23, the e, f, g, h, k, as they are in the area of the circuit arrangement by the local studio foreign horizontal synchronous

voltage according to FIGS. 1 and 2 occur. 25 pulses synchronized, whereas with a changeover

Fig. 1 shows a circuit arrangement for switching this switch to synchronize the dashed lines of a television studio, with all the circuit arrangements for synchronizing the pulse generator 1 used to bring about the setting of the local horizontal sync pulses k are not shown for the purpose of simpler representation.

Phase matching of the vertical sync pulses 30 Fig. 2 shows an embodiment of the push serving. According to Fig. 1, the local pulse generator 1 has a function generator 22 and the electronic phase an auxiliary mother generator 2, which with the help of the slide 13. Each time the switch 15 is actuated phase discriminator 3 either with the from the local through the switch 23 the mother generator not previously borrowed 4 originating or connected to the ground via the resistor 25 or 26 via terminal 5 supplied external television signal 35 (10 kÜ each) positively charged end of one of the consynchronized. capacitors 27 and 28 (j ^e 100 μ ¥) in the base circuit of the foreign television signal, the set of picture content transistor 29 (OC 141) to ground potential. Signals, blanking signals and sync pulses are sent to the base of the transom. This negative surge arrives at the base of the transampler, is sistor 29 via terminal 5 and blocks it until the condenser amplifier 6 and the amplitude filter 7 are connected to 27 and 28, respectively leads through the base resistor 31, which only lets the sync signals through. (22 kü) and via the resistor 32 (3.3 kÜ) so far In the separating stage 8 the vertical synchronous charge will have been reversed that the base potential has become a little more positive than the emitter potential from the horizontal synchronous pulses. Data disconnects and after these foreign horizontal sync pulses, the conductive (saturated) state on the one hand of the coincidence stage 9 and on the other hand the 45 state is immediately set again. The Zener diode 33 (Z 8) is fed to the gate circuit 11. The local nut stabilization of the clamp generator 4 applied via terminal 34 oscillates on the double horizontal of - 15 Volts. At the collector resistor 35 frequency and if precision offset operation is a (1 kü) then a positive voltage pulse appears, quartz oscillator with very high frequency accuracy. The integrating network, consisting of the frequency divider 12 connected downstream, takes place the 50 levels 36, 37, 38 (each 3.9 kÜ) and from the condensate conversion into horizontal-frequency pulses /, which sators 41, 42, 43 (each 25 [iF), and then pass through the electronic phase shifter 13. Via the impedance converter with the transistor 44 The output pulses of this phase shifter 13, (BCZ 11), the resistors 45 (1.5 kü), 46 (22 kü) ie the local horizontal sync pulses k, and the capacitor 47 (175 nF) for control On the one hand the coincidence stage 9 and on the other hand phase shifter 13 are used, on the other hand the gate circuit 14 is supplied. At the output of the phase shifter 13 consists of two in cascade coincidence circuit 9 only a pulse appears, connected monostable multivibrators. The one if the foreign and the local horizontal synchronous of these multivibrators consists of the transistors 51, impulse at the input of the coincidence circuit phase 52 (types 2 SA 17), of the resistors 53 (10 kü), moderately coincides. With the help of the ^{synchronizing switch 15 actuated manually from 6} ° 54 (270 kü), 55 (33 kü), 56 (1 kü), 57 (22 kü), the switching 58 (1 kü), 59 (10 kü) , also from the capacitors output signal of the coincidence circuit optionally a 61, 62 Qe 100 pF), 63 (2.5 nF), 64 (250 pF) and from the two inputs of the bistable vibrator 16 pulling diodes 65, 60 (of the type OA 72). The other conducts, which, together with the gate circuits 11 and 14 of these multivibrators, consists of the transistors 66, an electronic switch for the horizontal ⁵ 5 67 (types 2 SA 17), from the resistors 68, 69 forms synchronous pulses and only when there is coincidence (1 kü), 70 (22 kü), 71 (1 kü), 72 (5.6 kü), 73 (33 kü), this switches horizontal sync pulses. The 76 (250 pF) connected from the capacitors 74 (100 pF), 75 (2.5 nF) to the phase discriminator 3 and from the diode 77 (type OA 72). the

Terminals 78 are connected to the positive pole of a 6.5 volt voltage source. Terminal 81 is connected to the negative pole of a voltage source with -5 volts.

The first monostable multivibrator is synchronized by a series of horizontal-frequency pulses /. These are fed to the multivibrator via terminal 82 and come from the frequency divider 12. The edge g 'of the square-wave pulse sequence g generated in this first multivibrator is thus established. The second monostable multivibrator is via the diode 60 through the edge "g synchronized so that so that the pulse edge h 'of the pulse train results in h. Since the pulse e from both the resistor 57 to the first multivibrator and via the resistor 70 to the second multivibrator is supplied, g are a function of the bell-shaped curve of potential of the pulse e in the course of switching the pulse edges "and h" shifted. the pulse widths d of the pulse sequences g and h, which amounted to 0.25 D in the rest state, growing the maximum of the boost function e to 0.8 D. The total phase deviation of the output pulse k is thus 2 - (0.8-0.25) -D = 1.1 D, that is to say a little more than 360 °.

Claims (5)

PATENT CLAIMS: 1. A method for switching from one television signal to another, in particular from one synchronized by means of a local pulse generator to an incoming foreign television signal with practically the same synchronization frequency, characterized in that the phase of the horizontal synchronizing pulses (J) derived from the mother generator (4) of the local pulse generator at the initiation of each switching process once over a range of at least one period and independently of the instantaneous phase position of the external horizontal sync pulses is shifted with the help of a phase shifter and that at the moment of the temporal correspondence between external and local horizontal pulses, the actual switching in a known manner automatically by means an electronic switch (8, 11, 14, 16) takes place. 2. The method according to claim 1, characterized in that the horizontal sync pulses (/) the local mother generator (4) pass through an electronic phase shifter (13) which when each switching process is initiated, a control signal (e) is received which is dimensioned in this way is that the local horizontal sync pulses (/) are shifted at least one period. 3. The method according to claim 1 and 2, characterized in that the control signal (e) triggered at the initiation of each switching process has a - preferably bell-shaped - potential profile which rises from an initial value to a maximum value and then goes back to the initial value, and that the change in potential proceeds so slowly that the frequency deviation temporarily occurring during this process is very small compared to the horizontal ^{synchronous frequency - preferably smaller than χ} / ιοοο the horizontal synchronous frequency. 4. phase shifter for performing the method according to claim 2, characterized in that it consists of two monostable switching stages connected in cascade, the pulse widths of which are changed by the control voltage (e). 5. Phase shifter according to claim 4, characterized in that it consists of two monostable multivibrators connected in cascade, each of which is equipped with two transistors (51, 52 or 66, 67), and that the control voltage (s) each have the pulse width (d) the determining base circuit (over 57 or over 70) of these multivibrators is supplied as a supply voltage. Considered publications:
"Technical in-house communications of the NWDR", 1952, No. 9/10, p. 174. 1 sheet of drawings 1 309 510/185 2.