On screen tuning indicator device for television receiver

Claim 2

A tuning indicator device for a television receiver comprising: means for producing a voltage in accordance with the state of tuning which assumes a maximum value in the tuned state; means for developing a signal waveform having a slope, the frequency of which depends on the repetition frequency of an output of a deflection circuit; means for slicing said sloped waveform signal at upper and lower levels which are determined in accordance with said voltage; waveform shaping circuit means for generating a rectangular wave having a width corresponding to the length of the sloped portion of said sliced waveform; and means for indicating the rectangular wave derived from said waveform shaping circuit as a tuning signal on a screen of a picture tube of said television receiver.

Claim 3

A tuning indicator device for a television receiver according to claim 1, further comprising means for applying a rectangular wave derived from said waveform shaping circuit to a demodulator tube, thereby indicating the tuning signal on the screen of the picture tube.

Claim 4

A tuning indicator device for a television receiver according to claim 1, wherein said means for slicing said signal includes a transistor having a plurality of electrodes, to the base electrode of which is applied said voltage, a first resistor inserted between a first one of the remaining electrodes of said transistor and ground, a second resistor inserted between a second one of the remaining electrodes of said transistor and a power supply voltage, two diodes connected with said first and second remaining electrodes of said transistor in reverse polarity relationship with each other, the other ends of said two diodes being connected with each other; means for applying sawtooth waves at the connection point between said two diodes through a third resistor; and means for deriving a sliced signal from the connection point between said two diodes to generate a rectangular wave having a width corresponding to the length of the sloped portion of said sliced waveform.

Claim 5

A tuning indicator device for a television receiver according to claim 3, wherein the value for said third resistor is selected to be substantially larger than those for said first and second resistors.

Claim 6

A tuning indicator device for a television receiver according to claim 3, further including a clamping diode for clamping the sawtooth wave, said clamping diode being disposed between the end of said third resistor at which the sawtooth wave arrives and ground.

Claim 7

A waveform shaping circuit comprising: a transistor having first and second electrodes and a base electrode; said base electrode being connected with a voltage suppLying means for determining levels at which a sawtooth wave signal is sliced; a first resistor disposed between said first electrode and ground; a second resistor disposed between said second electrode and a power source; two diodes connected at their one ends with said first and second electrodes of said transistor in reverse polarity relationship with each other; a connection point at which the other ends of said two diodes are connected to each other, thereby constituting an output electrode of said circuit; and a third resistor connected to said connection point at its one end and having a resistance value which is substantially greater than those of said first and second resistors, the other end thereof being supplied with said sawtooth wave signal, whereby said sawtooth wave signal is sliced at upper and lower levels in accordance with a potential applied at said base electrode.

Claim 8

A waveform shaping circuit comprising: a transistor having first and second electrodes and a base electrode; said base electrode being connected with a voltage suppLying means for determining levels at which a sawtooth wave signal is sliced; a first resistor disposed between said first electrode and ground; a second resistor disposed between said second electrode and a power source; two diodes connected at their one ends with said first and second electrodes of said transistor in reverse polarity relationship with each other; a connection point at which the other ends of said two diodes are connected to each other, thereby constituting an output electrode of said circuit; and a third resistor connected to said connection point at its one end and having a resistance value which is substantially greater than those of said first and second resistors, the other end thereof being supplied with said sawtooth wave signal, whereby said sawtooth wave signal is sliced at upper and lower levels in accordance with a potential applied at said base electrode.