VIDEO BLANKING AND SOUND MUTING CIRCUIT

• US 3,673,318 A
• Filed: 02/03/1971
• Issued: 06/27/1972
• Est. Priority Date: 02/03/1971
• Status: Expired due to Term

• Current Assignee: RCA Corporation
• Original Assignee: Pak Chong Tang, Perry Charles Olsen
• Inventors: Olsen, Perry Charles, Tang, Pak Chong
• Primary Examiner(s): Richardson, Robert L.
• Application Number:
  US05/112,178
• Time in Patent Office: 510 Days
• Field of Search: 178/5.8R,7.3R
• US Class Current: 348/633
• CPC Class Codes: H03G 3/348 Muting in response to a mechanical action or to power supply variations, e.g. during tuning; Click removal circuits
• CPC Class Codes: H03J 5/10 Settings determined by a number of positioning means mounted on a common support, e.g. turret tuner, which is adjustable to desired positions, a different positioning means being in operation in each position
• CPC Class Codes: H04N 5/505 Invisible or silent tuning

Abstract

A switching circuit, dependent solely on the value of fixed impedances and supplied direct current voltages, blanks the picture and mutes the sound of a television receiver during its channel selection tuning, either manually or automatically by remote control.

Claims

1. A video blanking and sound muting circuit for a television receiver having a manually operated detenting channel selector and effective upon manual operation of said selector to deactivate the video and sound reproduction systems of said receiver during channel changing, comprising:

first and second potential sources;

a plurality of relatively fixed impedances serially coupled between said sources and forming at least one junction point Therebetween;

first and second rectifier means respectively coupling said junction point to control terminals of each of said video and sound reproduction systems to regulate the operations thereof during said channel changing;

a first switch means coupled to the junction between a first and second of said plurality of impedances and operative in conjunction with said detenting channel selector to modify the serial coupling between said first and second potential sources when said selector is manually changed to an undesired channel to establish a first direct voltage condition at said junction point; and

a second switch means coupled to the junction between said second and a third of said plurality of impedances and operative in conjunction with said detenting channel selector to additionally modify the serial coupling between said first and second potential sources when said selector is manually changed between adjacent channels to establish a second, different direct voltage condition at said junction point;

said first and second potential sources and said first, second and third fixed impedances being selected such that either of said first and second direct voltage conditions is sufficient to bias at least one of said rectifier means in a direction to de-activate its associated video or sound reproduction system and such that a third direct voltage condition is developed at said junction point in the absence of said selector being manually changed to an undesired channel or between adjacent channels which is sufficient to bias both of said rectifier means in a direction to activate both their associated video and sound reproduction systems during this normal operative mode of said television receiver.

2. The circuit of claim 1 for use in a television receiver also having an electric motor adapted to drive the channel selector under a remote control order, wherein said circuit additionally includes:

third rectifier means coupled to said junction point formed on said plurality of relatively fixed impedances; and

means, including a third switch means coupled to said third rectifier means, for biasing said third rectifier means in response to the energization of said motor by the giving of said remote control order in a direction to establish a direct voltage condition at said junction point sufficient to bias at least one of said first and second rectifier means in a direction to de-activate its associated video or sound reproduction system when said order is given and for biasing said third rectifier means in response to the de-energization of said motor by the absence of said remote control order in a direction to establish another direct voltage condition at said junction point sufficient to bias both of said first and second rectifier means in a direction to activate both their associated video and sound reproduction systems when said order is absent during the normal operative mode of said television receiver, whereby at least one of the video and sound reproduction systems of said receiver is further de-activated during remote control channel changing.

3. The circuit of claim 1 wherein said first and second potential sources are serially coupled by first, second and third impedances, wherein said first switch means is operative in conjunction with said detenting channel selector to bypass said first impedance when said selector is manually changed to an undesired channel, and wherein said second switch means is operative in conjunction with said detenting channel seLector to shunt a fourth relatively fixed impedance across said third impedance when said selector is manually changed between adjacent channels, such that selection of said first and second potential sources and of said first, second, third and fourth impedances establish each of said direct voltage conditions at the junction point of said second and third impedances.

4. The circuit of claim 3 wherein said first and second direct voltage conditions developed at the junction point of said second and third impedances forward bias at least one of said first and second rectifier means in a direction to de-activate their associated video and sound reproduction systems and wherein said third direct voltage condition developed at said junction point reverse biases both of said first and second rectifier means in a direction to activate both their associated video and sound reproduction systems.

5. A video blanking and sound muting circuit for a television receiver having a manually operated detenting channel selector and effective upon manual operation of said selector to de-activate the video and sound reproduction systems of said receiver during channel changing, comprising:

first and second potential sources of opposite polarity;

first, second and third resistors serially coupled between said sources;

a first rectifier coupling the junction between said second and third resistors to a control terminal of said sound reproduction system to regulate its operation during said channel changing;

a second rectifier coupling said junction between said second and third resistors to a control terminal of said video reproduction system to also regulate its operation during said channel changing;

a first switch means having one contact coupled to the junction between said first and second resistors and another contact coupled to a point of reference potential, with said first switch means being operative in conjunction with said detenting channel selector to establish a first direct voltage condition at the junction of said second and third resistors when said selector is manually changed to an undesired channel;

a fourth resistor having one terminal thereof coupled to said second source of potential; and

a second switch means having one contact coupled to the junction of said second and third resistors and another contact coupled to a second terminal of said fourth resistor, with said second switch means being operative in conjunction with said detenting channel selector to establish a second direct voltage condition at said junction point between said second and third resistors when said selector is manually changed between adjacent channels;

the manual changing of said detenting channel selector to an undesired channel and between adjacent channels cooperating to connect said contacts of said first and second switch means, respectively, such that said switch connections together with the values of said first and second potential sources and said first, second, third and fourth resistors establish said first and second direct voltage conditions at magnitudes sufficient to bias at least one of said first and second rectifiers in a direction to de-activate its associated video or sound reproduction system and such that a third direct voltage condition is developed at the junction point of said second and third resistors in the absence of said selector being manually changed to an undesired channel or between adjacent channels of a magnitude sufficient to bias both of said first and second rectifiers in a direction to activate both their associated video and sound reproduction systems during this normal operative mode of said television receiver.

6. The circuit of claim 5 wherein a fifth resistor is included to couple said junction between said second and third resistors to the cathode of said first rectifier, the anode of which is coupled to said sound reproduction system control terminal, wherein a sixth resistor is included to couple said Junction between said second and third resistors to the cathode of said second rectifier, the anode of which is coupled to said video reproduction system control terminal, and wherein a first capacitor is included to couple the cathode of said first rectifier to said point of reference potential.

7. The circuit of claim 6 for use in a television receiver also having an electric motor adapted to drive the channel selector under a remote control order, wherein said circuit additionally includes:

seventh and eighth resistors serially coupled between said first potential source and said point of reference potential;

a third rectifier;

a third switch means;

ninth and tenth resistors respectively coupling said third rectifier to said third switch means and to said junction between said second and third resistors;

a second capacitor coupling the junction of said third rectifier and said tenth resistor to said point of reference potential;

such that energization of said motor to effect channel changing in response to the giving of said remote control order establishes a direct potential at the junction of said third rectifier and said second capacitor sufficient to bias at least one of said first and second rectifiers in a direction to de-activate its associated video or sound reproduction system when said order is given and such that said third rectifier is biased by said seventh and eighth resistors in the absence of said remote control order being given to establish another direct potential at the junction of said second and third resistors which is sufficient to bias both of said first and second rectifiers in a direction to activate both their associated video and sound reproduction systems during the normal operative mode of said television receiver, whereby at least one of the video and sound reproduction systems of said receiver is further de-activated during remote control channel changing.

8. The circuit of claim 7 wherein said eighth and ninth resistors are selected to provide said first direct potential at the junction of said third rectifier and said second capacitor of a value sufficient to bias at least one of said first and second rectifiers in a direction to de-activate its associated video and sound reproduction system when said remote control order is given.

9. The circuit of claim 8 wherein said seventh resistor is selected of a value to cooperate with said first potential source and said eight resistor to bias said third rectifier in the absence of said remote control order being given such that both of said first and second rectifiers become biased in directions to activate both their associated video and sound reproduction systems in the absence of said order.

10. The circuit of claim 9 wherein said tenth resistor is selected of a value such that the potential developed across said second capacitor and coupled to the junction of said second and third resistors will, in conjunction with said first, second, third, fourth, fifth, and sixth resistors and said first and second potential sources, bias both of said first and second rectifiers in a direction to de-activate their associated video and sound reproduction systems when said remote control order is given.