DE2422908B2 - RADIO OR TELEVISION RECEIVER WITH ELECTRONIC TUNING - Google Patents

Description

For radio and television receivers, it is z. B. from DT-AS 17 66 611 known to integrate a station search circuit into the circuit structure with the task of always tuning the automatic tuning system to a station and keeping it optimal when certain reception requirements - z. B. sufficient field strength or a sufficient signal / noise ratio - are given.

Such automatic search functions, whose basic mode of operation is based on a block diagram in F i g. 1 is shown by pressing a special search pulse button 1 on the receiving device 2 started and after the electronically performed vote of the 3 with the help of a sawtooth generator Receiving part 4 to the nearest worthy transmitter in the receiving band, by one after Completion of the tuning process in the demodulator part 5 generated stop pulse 6 automatically stopped.

In the arrangement according to Fig. 1, the operator of the device must press key 1 again and again, if the perceived content of the automatically set program does not meet his expectations is equivalent to. This repeated manual touching can be done with the previously known ones, predominantly in car radios used transmitter search circuits, especially in tense road traffic, an increased safety risk mean.

In the case of stationary receivers with a station search, the need to be repeated continuously Touching is also disadvantageous because the operator has to stay at the device without interruption until a desired program is found.

It is the object of the invention to avoid repeatedly having to touch the Suclilauf start button and thus, in addition to increasing the ease of use, to reduce the safety risk in the case of the car receiver. The invention relates to a radio or television receiver in which a sawtooth generator, which can be switched on with a start button, is provided for electronic tuning with capacitance diodes and in which the sawtooth generator is stopped by a stop pulse obtained from the demodulator, in such a way that the attuned tuning is maintained and lies therein that the stop pulse is also fed to a monostable multivibrator 10, the output of which is connected to the line for the start pulse. in such a way that after a time given by the time constant of the flip-flop a start pulse 8 is delivered to the sawtooth generator and that another contact \ b is provided on the start button, with which the flip-flop can be reset.

The circuit according to the invention ensures that after the search run start function has been triggered, reception and playback of the station tuned by the electronic automatic search only one certain adjustable time is given and that after this time the receiving part automatically switches to the is tuned to the next technically receivable station. A further development of the invention is that in the line for feeding the Haltimpi'lses to the flip-flop a switch U is used to enable a selection between normal and interval search. Finds the user within the pre-set period of time, which is, for example, about 3 seconds, enjoyment of the program, he can switch to the next search by switching back this "Interval Normal" key 11 prevent.

The function according to the invention is shown in the circuit according to FIG. 2 shown. This replaces the lower part of the circuit between points A and B of FIG. 1, which is used in the usual HF tuning schemes with capacitance diodes to generate the sawtooth voltages required for automatic tuning of the reception area, by a structure that is expanded according to the invention.

In the circuit according to the invention according to FIG. 2 is a sawtooth generator 3 of a known type in terms of circuitry combined with a timer 10 and a manually operated double button 1 and is shown in Function set when a separate operating mode switch 11 moves from position 11a "normal" to position 11 /> »Interval« is switched. The timer 10 can be a triggerable monolithically integrated monoflop. This has a trigger input 10a, a Reset input lOfe and a switching output 10c.

After pressing button 1, the automatic transmitter search runs via the now closed contact la in the manner described for FIG. 1, since the sawtooth generator is started via input 3a. At the same time, the time memory 10 is reset by the contact 16, which also closes. The pulse 6 arriving from the demodulator via B after optimal transmitter tuning stops the further increase in voltage in the sawtooth generator in the usual way via the input 36 and simultaneously starts the timer 10 via the contact Ha of the operating mode switch 11 and the trigger input 10a.

After the arrival of a trigger pulse at the input 10a, the minus potential at the output 10c changes to the plus potential in this timer 10 for a time At which can be preselected on a trimmer 7 within certain limits. The diode 9 blocks a signal supply in this potential position of the output 10c.

tion in the input 3a of the sawtooth generator 3.

After the preset time Jf has elapsed, the monoflop tilts back and the output 1Or picks up again Minus potential. This makes the diode 9 conductive and the sawtooth generator 3 through a negative one Pulse started again. With increase or decrease: · that of The voltage generated by the receiver circuit 4, 5 is tuned to the next following transmitter.

This process repeats itself periodically as long as until the selector switch 11 is out of contact position 11 ;; ("Interval") in the position 11 £> ("Normal") is brought. In this position, the tuned transmitter held indefinitely. Characteristic time-dependent processes are shown in FIG. 3 for one adopted Functional sequence shown graphically over a longer period of time.

The described switching combination from FIGS. 1 and 2 offers the practical possibility of quickly moving through the reception area in "normal" mode by continuously pressing the pulse button or in "interval" mode. to end the dwell time Δι by briefly tapping the l button and to initiate the selection of the next station.

Another advantage of the circuit design according to the invention is that one after the Switching on the device from manual tuning, the remaining receiver misalignment after switching the search mode is canceled immediately.

According to the invention it is further proposed that the Time constant of the flip-flop 10 is designed to be manually adjustable. There is thus the possibility of the Dwell time of the station played in the interval mode according to the individual wishes of the Adjust the operator.

For this purpose 2 sheets of drawings

Claims (3)

Patent claims: 1. Radio or television receiver in which a sawtooth generator that can be switched on with a start button is provided for electronic tuning with capacitance diodes and in which the sawtooth generator is stopped by a stop pulse obtained from the demodulator, in such a way that the attunement is maintained, characterized in that the hold pulse is additionally fed to a monostable multivibrator (10), the output of which is connected to the line for the start pulse, in such a way that after a time given by the time constant of the multivibrator, a start pulse (8) is delivered to the sawtooth generator and that the start button Another contact (\ b) is provided, with which the flip-flop can be reset. 2. Receiver according to claim 1, characterized in that that in the line for supplying the stop pulse to the flip-flop a switch (11) is used to enable a selection between normal and interval search. 3. Receiver according to claim I or 2, characterized in that the time constant of the trigger circuit (10) is designed to be manually adjustable.