JPS5856517A - Channel selector - Google Patents

Abstract

PURPOSE:To avoid the reception from being made unable due to malfunction of an automatic frequency adjusting circuit with an unnecessary signal and the re-application of an original signal, when the reception signal is tentatively interrupted, by using a discrimination circuit and a latch circuit. CONSTITUTION:A discriminating circuit 8 which discriminates that a reception signal is within a virtual tuning range at the outside of the tuning range from a discriminated output from an automatic frequency adjusting circuit, is provided and at the generation of the discriminated output, a preset tuning signal of a memory provided in a channel selection circuit 1 is forcedly read out and the tuning point is fixed. A latch circuit 9 is set and the operation of the automatic frequency adjusting circuit is stopped with the latch output. Thus, even if the supply of a television signal during the reception is interrupted due to any cause, the reception caused by the supply of the original signal again due to malfunction of the automatic frequency adjusting circuit by an unnecessary signal is prevented from being made unable.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a channel selection device, and more particularly to a channel selection device that prevents channel selection failures due to the operation of an automatic frequency adjustment circuit when a television signal is interrupted.

In recent years, with the rapid development of video tape recorders,
Video tape recorders are increasingly being connected to television receivers. In this case, the video tape recorder is provided with a changeover switch for switching between video and television, and by operating this changeover switch, it is possible to change over between the reception output of the television signal and the video playback output.

However, if the above-mentioned short switch is operated while the TV receiver is receiving channel 8, for example, when the signal is not input to the TV receiver, the switch installed in the TV receiver is・A malfunction occurs in the automatic frequency adjustment circuit. The automatic frequency adjustment circuit commands the discrimination characteristics shown in Figure 1, detects that the discrimination output is located between Vl and VS, and determines that it is located in zone A, which is the normal tuning range. are doing.

In this case, the above-mentioned discrimination output characteristic has a zone B as a tuning range, which is located on both sides of the person, and a zone D and B showing a tuning state outside of the non-tuning range 0.
As a result, if, for example, the received signal is cut off by operating the changeover switch provided on the video tape recorder while a certain channel is being received at point α.

Along with this, β shifts from zone A as the tuning range.
At this point, the RF' modulator of a nearby television signal, such as a video tape recorder, has two channels (9.7125 MHz).
), unnecessary waves such as the second harmonic of the video carrier wave may appear. At this time, the automatic frequency adjustment circuit detects that the discrimination output deviates from the reference range vl-vl and operates, and performs an operation to pull the signal at point β so that it is located at the zone person, and accordingly α The signal at point moves to point r.0 Next, when the signal of the original reception channel that was cut off is supplied, the tuning point for the original reception signal has already moved from point α to point r. , the pull-in operation is stopped as the discrimination output for this signal is located within the range ①i to v3. Therefore, the original received signal becomes a signal included in zone D, which is largely shifted from zone A as the tuning range, and the image is no longer displayed, resulting in a noise screen being reproduced.

Therefore, one object of the present invention is to provide a channel selection device that prevents the automatic frequency adjustment circuit from malfunctioning due to an unnecessary signal when the received signal is temporarily interrupted, and from malfunctioning in which reception becomes impossible when the original signal is supplied again. It is to provide.

In order to achieve such an object, the present invention provides a discrimination circuit that distinguishes between Zone A, which is the tuning range, and Zones E and D, which are the pseudo tuning ranges. The contents of the memory for the original received signal provided in the station circuit are read out and the channel selection is performed. Hereinafter, the channel selection device according to the present invention will be explained in detail using the drawings.

FIG. 2 is a circuit diagram showing an embodiment of the channel selection device according to the present invention. In the figure, l is a channel selection circuit, and the addresses opposite to the channel selection switches 28 to 2 in the internal memory (not shown) are used to control tuning to preset reception channels. The tuning signal is stored as a digital signal.

3 is a tuning circuit which converts the tuning signal designated and read by the output of each channel selection switch 21 to 21 into a voltage signal and controls the tuner part 4 by using the tuning voltage input outputted from the channel selection circuit 1 as an input. The control path 5 is a television receiver which receives the output of the tuner part 4. On the other hand, the discrimination output B output from the tuner part 4 is compared with the upper and lower limit values in the window comparator 6, and if it exceeds the upper limit 1, it outputs a signal O1, and if it is below the lower limit value In this case, the signal C8 is sent out and supplied to the tuning circuit 1, thereby providing the tuning circuit 1 with information on the direction of deviation of the tuning point and the gradation of the deviation. 7 is horizontal synchronization signal HD and 7 rhinos FBP
8 is a discrimination circuit which detects the absence of either of them and generates a comparison output Dtl. By detecting that a verification signal is supplied from the verification circuit 7, a pseudo tuning range 70. It is determined that the signal is located at E, and the determined output E is supplied to the tuning circuit 1 to instruct the internal memory to output the tuning signal when selecting the original signal. Reference numeral 9 denotes a latch circuit that is set by the discrimination circuit 8 and reset by the output of an OR gate 10 which receives the outputs of the channel selection switches 2a to 2J as input, and the latch signal F output from the latch circuit 9 is as follows: The signal is supplied to the tuning circuit 1 and instructs to cancel the automatic frequency adjustment operation.

In the nine-channel selection device configured as described above, when any of the channel selection switches 2a to 21 is operated, the output of the operated channel selection switch selects a predetermined value in the memory provided in the channel selection circuit. The address is specified and its contents are read. In this case, tuning information of preset channels is stored in the memory corresponding to each channel selection switch 2a to 2M. Therefore, the tuning information read from the memory is supplied to the tuning control circuit 3 after being converted into a tuning voltage A as a voltage value. The tuning control circuit 3 supplies the received television signal corresponding to the preset channel to the television receiver section 5 by moving the tuning point of the tuner section 4 in accordance with the input tuning voltage value.

In this case, the discrimination output B indicating the tuned state generated from the tuner part 4 is set to the upper limit value v1. It is compared with the lower limit iVm, and the upper and lower limit values V, -V,
If it is located within the range of , it continues to maintain that state as being located within the tuning range. On the other hand, when the received signal shifts to a frequency lower than the tuning range, the discrimination output B rises beyond the upper limit value v1, so the win P converter 6 sends a signal C! corresponding to the amount of the excess. is generated,
If the reception frequency shifts by nine to the higher side, a signal 01 corresponding to the amount of shift is generated.

Therefore, the tuning circuit 1 inputs the signals of, o generated from the window comparator 6, determines the amount and direction of the deviation, and performs control to bring the signal into the tuning range.

Next, the verification circuit 7 verifies the horizontal synchronizing signal HD and the fly mark pulse FBP, and when either one is lost, it assumes that the television signal supply is IMWIT and generates a verification output. On the other hand, the discrimination circuit 8 detects the presence of the signal AI when the verification output signal is supplied, and detects the presence of the signal A when the verification output signal is generated.
The fact that , A, and A are not present means that there is no unnecessary reception (g signal) in zone D and Fi, which indicate the pseudo-same range shown in the diagram. .

When the channel selection circuit 1 is supplied with the discrimination signal E, the memory address at the time of reception of the original preset channel is forcibly read out, thereby presetting the channel to the original reception channel again.

Further, when the discrimination circuit 8 generates the discrimination signal E.

The latch circuit 9 is latched and generates a latch signal F.

This latch signal F is supplied to the tuning circuit 1 and instructs to stop the automatic frequency adjustment operation, thereby continuing to maintain the originally set tuning state. Then, when the television signal that was cut off earlier is supplied again, this signal will be tuned at the optimal tuning point 9, and thus optimal image reception will soon be obtained.

Next, use the channel selection switches 2a to 21 to
When a round channel is designated, an output is generated from the OR gate 10 and the latch circuit 9 is reset, thereby causing the automatic frequency aif! The order to stop L.I.I. has been lifted.1
The station circuit 1 is returned to normal operation.

As explained above, the tuning device according to the present invention is provided with a discrimination circuit that discriminates from the discrimination output output from the automatic frequency adjustment circuit that the received signal belongs to the pseudo tuning range that deviates from the tuning range, and generates a discrimination output. Sometimes, the preset tuning signal in the memory provided in the tuning circuit is forcibly read out to fix the tuning point, and a latch circuit is set to control the operation of the automatic frequency adjustment circuit to be stopped using the latch output. be. Therefore, even if the supply of the TV signal being received is interrupted for some reason, the automatic frequency adjustment circuit will malfunction due to the unnecessary signal, making reception impossible when the original signal is supplied again. It has an excellent effect in solving problems.

[Brief explanation of the drawing]

FIG. 1 is a discrimination characteristic diagram of a tuning signal, and FIG. 2 is a circuit diagram showing an embodiment of a tuning device according to the present invention. DESCRIPTION OF SYMBOLS 1... Tuning circuit, 2a-2... Channel selection switch, 3... Tuning control circuit, 4... Tuner part, 6... Win P controller, 7... Verification circuit , 8... Discrimination circuit, 9... Latch circuit, 10
...or gate.

Claims (1)

[Claims] (1) By controlling the tuning circuit using the discrimination output output from the automatic frequency adjustment circuit, the television signal can be tuned to the nine preset channels specified by the channel selection switch. a discrimination circuit that determines that the received signal is an unnecessary signal and is located in the pseudo tuning range by detecting a condition indicating that the discrimination output belongs to the tuning range without the presence of and a latch circuit that is reset by the output of any one of the channel selection switches, and supplies the discrimination output of the discrimination circuit to the channel selection circuit to designate the nine channels that are received first; A channel selection device characterized in that an output of a latch circuit issues a command to stop the operation of an automatic frequency II adjustment circuit.