Mode recognition for vertical countdown

Claim 2

In a method for vertical synchronization of a television system which digitally locally develops vertical sync pulses, derives vertical sync pulses from a received television signal, and selectively applies the locally developed sync pulses or the derived sync pulses to a vertical sweep system of the television system, the improvement comprising the steps of: defining a time window having a beginning and an end; accumulating a count of the derived sync pulses occurring within said time window; resetting said count of derived vertical sync pulses to a preset starting count in response to the end of said time window; determining whether fewer than a predetermined number of said derived sync pulses occur within said time window; said determining step including toggling a logic device in response to the beginning of said time window; and if said determining step indicates that fewer than said predetermined number of derived sync pulses occur within said time window, then triggering said logic device to generate a signal in response to the end of said time window and signaling said television system to apply said locally developed sync pulses to said vertical sweep system.

Claim 3

The method of claim 1 wherein said step of defining a time window includes accumulating a count of vertical field time intervals and said resetting step comprises resetting said count of desired vertical sync pulses when the count of vertical field time intervals reaches a predetermined number.

Claim 4

The method of claim 1 including disabling said logic device when said count of derived vertical sync pulses reaches said predetermined number of said derived vertical sync pulses.

Claim 5

In a method for vertical synchronization of a television system which digitally locally develops vertical sync pulses, derives vertical sync pulses from a received television signal, and selectively applies the locally developed sync pulses or the derived sync pulses to a vertical sweep system of the television system, the improvement comprising: maintaining a first count representing accumulated vertical field time intervals and resetting said count periodically. maintaining a second count representing accumulated derived vertical sync pulses; resetting said second count in response to said first count reaching a first predetermined number; toggling a logic device in response to said first count reaching said first predetermined number; resetting said logic device in response to said second count reaching a second predetermined number; and signaling said television receiver to apply the locally developed sync pulses in response to said logic device being toggled to a predetermined one of its states, whereby said signaling will occur unless said second predetermined number of derived sync pulses is reached before said first predetermined number is reached.

Claim 6

In a method for vertical synchronization of a television system which digitally locally develops vertical sync pulses, derives vertical sync pulses from a received television signal, and selectively applies the locally developed sync pulses or the derived sync pulses to a vertical sweep system of the television system, the improvement comprising: maintaining a first count representing accumulated vertical field time intervals and resetting said count periodically. maintaining a second count representing accumulated derived vertical sync pulses; resetting said second count in response to said first count reaching a first predetermined number; toggling a logic device in response to said first count reaching said first predetermined number; resetting said logic device in response to said second count reaching a second predetermined number; and signaling said television receiver to apply the locally developed sync pulses in response to said logic device being toggled to a predetermined one of its states, whereby said signaling will occur unless said second predetermined number of derived sync pulses is reached before said first predetermined number is reached.

Claim 7

In a method for vertical synchronization of a television system which digitally locally develops vertical pulses, derives vertical sync pulses from a received television signal, and selectively applies the locally developed sync pulses or the derived sync pulses to a vertical sweep system of the television system, the improvement comprising: detecting noise in said received signal including defining a first time window during each of a plurality of vertical fields, detecting any of said derived vertical sync pulses from said received television signal which occur during said first time window, and actuating a logic device to provide a noisy signal indication in response to the detection of said pulses during said first time window; detecting a low sync pulse signal strength in said received signal, including defining a second time window having a relationship to the vertical sync frequency of the television system, detecting any of the derived vertical sync pulses which occur during said second time window and an absence of a first predetermined number of said derived vertical sync pulses which occur during said second time window, and actuating said logic device in response to the detection of said absence of pulses; and signalling said television system to apply said locally generated sync pulses to said vertical sweep system in response to said logic device being actuated, whereby the logic device is used for signaling a condition when either the noise or low signal strength is detected.

Claim 8

In a method for vertical synchronization of a television system which digitally locally develops vertical pulses, derives vertical sync pulses from a received television signal, and selectively applies the locally developed sync pulses or the derived sync pulses to a vertical sweep system of the television system, the improvement comprising: detecting noise in said received signal including defining a first time window during each of a plurality of vertical fields, detecting any of said derived vertical sync pulses from said received television signal which occur during said first time window, and actuating a logic device to provide a noisy signal indication in response to the detection of said pulses during said first time window; detecting a low sync pulse signal strength in said received signal, including defining a second time window having a relationship to the vertical sync frequency of the television system, detecting any of the derived vertical sync pulses which occur during said second time window and an absence of a first predetermined number of said derived vertical sync pulses which occur during said second time window, and actuating said logic device in response to the detection of said absence of pulses; and signalling said television system to apply said locally generated sync pulses to said vertical sweep system in response to said logic device being actuated, whereby the logic device is used for signaling a condition when either the noise or low signal strength is detected.

Claim 9

The method of claim 5 wherein said step of defining a first time window comprises: initializing a counter at the beginning of each of said vertical fields and accumulating a count during each of said vertical fields; decoding a first value of said count accumulated by said counter; enabling said first time window in response to said decoding said first value; decoding a second value of said count of said counter; and disabling said first time window in response to decoding said second value.

Claim 10

The method of claim 5 wherein said step of defining a second time window includes accumulating a count of vertical field time intervals and resetting said count when it reaches a second predetermined number.

Claim 11

The method of claim 7 wherein said step of detecting any of said derived vertical sync pulses which occur during said second time window includes accumulating a count of any of said derived pulses which occur during said second time window.

Claim 12

The method of claim 8 further including resetting said count of derived sync pulses to a preset starting count at the close of said second time window.

Claim 13

The method of claim 9 wherein said step of detecting a low signal strength includes enabling a further logic device in response to the opening of said second time window and triggering said further logic device to generate a signal when said second time window closes.

Claim 14

The method of claim 10 further including disabling said further logic device when said count of said derived vertical sync pulses reaches said first predetermined number of said derived sync pulses.

Claim 15

The method according to claim 11 including resetting said count of derived pulses in response to said count of vertical field time intervals reaching said second predetermined number; toggling said further logic device in response to said count of vertical field time intervals reaching said second predetermined number; resetting said further logic device to one state in response to said count of derived pulses reaching said first predetermined number; and signaling said television system in response to said further logic device reaching another state, whereby said signaling will occur unless said first predetermined number of derived sync pulses is detected before said second predetermined number of vertical fields is detected after said further logic device is reset.

Claim 16

In a vertical synchronization system for a television system which digitally locally develops vertical sync pulses and derived vertical sync pulses from a received television signal and includes means for selectively applying the locally developed sync pulses or the derived sync pulses to a vertical sweep system of the television, the improvement comprising: means for defining a time window having a beginning and an end, said means for defining a time window including means for accumulating a count of vertical field time intervals and means for resetting said count when it reaches a predetermined number; means for detecting derived vertical sync pulses which occur during said time window and for detecting whether a predetermined number of said derived vertical sync pulses occur during said time window, said means for detecting including means for accumulating a count of derived vertical sync pulses occurring during said time window and means for resetting said count of derived vertical sync pulses to a preset starting count at the close of said time window; means responsive to said means for detecting for signaling said television system to apply said locally developed sync pulses to said vertical sweep system; said means for detecting including a logic device, means for enabling said logic device in response to the beginning of said time window and for triggering said logic device to generate a signal when said time window ends.

Claim 17

In a vertical synchronization system for a television system which digitally locally develops vertical sync pulses and derived vertical sync pulses from a received television signal and includes means for selectively applying the locally developed sync pulses or the derived sync pulses to a vertical sweep system of the television, the improvement comprising: means for defining a time window having a beginning and an end, said means for defining a time window including means for accumulating a count of vertical field time intervals and means for resetting said count when it reaches a predetermined number; means for detecting derived vertical sync pulses which occur during said time window and for detecting whether a predetermined number of said derived vertical sync pulses occur during said time window, said means for detecting including means for accumulating a count of derived vertical sync pulses occurring during said time window and means for resetting said count of derived vertical sync pulses to a preset starting count at the close of said time window; means responsive to said means for detecting for signaling said television system to apply said locally developed sync pulses to said vertical sweep system; said means for detecting including a logic device, means for enabling said logic device in response to the beginning of said time window and for triggering said logic device to generate a signal when said time window ends.

Claim 18

The improvement of claim 13 wherein said means for detecting includes means for determining if fewer than a predetermined number of derived vertical sync pulses occur during said time window.

Claim 19

The improvement of claim 13 further including means for disabling said logic device when said count of derived vertical sync pulses reaches said predetermined number.

Claim 20

In a vertical synchronization system for a television system which digitally locally develops vertical sync pulses and derived vertical sync pulses from a received television signal and includes means for selectively applying the locally developed sync pulses or the derived sync pulses to a vertical sweep system of the television, the improvement comprising: means for defining a time window having a beginning and an end, said means for defining a time window including means for accumulating a first count of vertical field time intervals and means for resetting said count when it reaches a first predetermined number; means for detecting derived vertical sync pulses which occur during said time window and for detecting whether a second predetermined number of said derived vertical sync pulses occur during said time window; and means responsive to said means for detecting for signalling said television system to apply said locally developed sync pulses to said vertical sweep system; said means for detecting including a logic device, means for enabling said logic device in response to the beginning of said time window and for triggering said logic device to generate a signal when said time window ends, said means for defining including a first counter coupled to receive signals at the vertical field rate and providing said first count and means for resetting said first counter periodically; said means for detecting including a second counter coupled to receive the derived vertical sync pulses, means for resetting said second counter in response to said first count reaching said first predetermined number, said logic device having at least two states, means for toggling said logic device in response to said first count reaching said first predetermined number, means for resetting said logic device to one state in response to said second counter reaching said second predetermined number, said logic device providing an output to said means for signaling said television system in response to said logic device reaching another state, whereby said signalling occurs unless said second predetermined number of derived sync pulses is counted before said first number of vertical field time intervals is counted after said logic device is reset.

Claim 21

In a vertical synchronization system for a television system which digitally locally develops vertical sync pulses and derived vertical sync pulses from a received television signal and includes means for selectively applying the locally developed sync pulses or the derived sync pulses to a vertical sweep system of the television, the improvement comprising: means for defining a time window having a beginning and an end, said means for defining a time window including means for accumulating a first count of vertical field time intervals and means for resetting said count when it reaches a first predetermined number; means for detecting derived vertical sync pulses which occur during said time window and for detecting whether a second predetermined number of said derived vertical sync pulses occur during said time window; and means responsive to said means for detecting for signalling said television system to apply said locally developed sync pulses to said vertical sweep system; said means for detecting including a logic device, means for enabling said logic device in response to the beginning of said time window and for triggering said logic device to generate a signal when said time window ends, said means for defining including a first counter coupled to receive signals at the vertical field rate and providing said first count and means for resetting said first counter periodically; said means for detecting including a second counter coupled to receive the derived vertical sync pulses, means for resetting said second counter in response to said first count reaching said first predetermined number, said logic device having at least two states, means for toggling said logic device in response to said first count reaching said first predetermined number, means for resetting said logic device to one state in response to said second counter reaching said second predetermined number, said logic device providing an output to said means for signaling said television system in response to said logic device reaching another state, whereby said signalling occurs unless said second predetermined number of derived sync pulses is counted before said first number of vertical field time intervals is counted after said logic device is reset.