Test signal generator for producing test patterns for a television receiver

Claim 2

Test signal-generating apparatus for producing test patterns for a television receiver of the type employing a pair of signalreceiving terminals for connection to an antenna, an imagereproducing device and scanning apparatus for scanning said device in first and second directions at respective first and second recurrence rates, said generating apparatus comprising means for deriving synchronizing signals from said scanning apparatus, pulse-generating means responsive to said synchronizing signals for producing pulses recurring in predetermined relation with respect to said first and second recurrence rates, and switching means coupled to said pulse-generating means and adapted for connection between said antenna and said pair of signal-receiving terminals for providing a low impedance across said receiving terminals in response to pulses produced by said pulse generating means.

Claim 3

Test signal-generating apparatus in accordance with claim 1 wherein said pulse-generating means is arranged for producing voltage pulses in timed relation determined by said first and second recurrence rates and of an amplitude greater than the voltage applied to said receiving terminals by signals received at said antenna, said switching means comprising voltage-responsive means insensitive to signal voltages from said antenna but responsive to said pulses of greater amplitude than said signal voltages to provide said low impedance.

Claim 4

Test signal-generating apparatus in accordance with claim 2 wherein said switching means comprises a diode adapted to be coupled across said receiving terminals poled to conduct upon the occurrence of pulses by said pulse-generating means.

Claim 5

Test signal-generating apparatus in accordance with claim 3 wherein said pulse-generating means produces first and second trains of pulses having respective recurrence rates equal to integral multiples of said first and second recurrence rates.

Claim 6

Test signal-generating apparatus in accordance with claim 4 wherein said first recurrence rate is equal to said line scanning rate and said first and second trains of pulses have respective recurrence rates equal to an integral multiple of said line-scanning rate and equal to an integral submultiple of twice said line-scanning rate.

Claim 7

Test signal-generating apparatus in accordance with claim 5 wherein said synchronizing signals recur at the line-scanning rate employed in said receiver.

Claim 8

Test signal-generating apparatus in accordance with claim 6 wherein said pulse-generating means comprises means responsive to simultaneous occurrence of pulses in said first and second trains of pulses for supplying a switching signal to said diode.

Claim 9

Test signal-generating apparatus in accordance with claim 7 wherein said first recurrence rate is equal to the line-scanning rate employed in said receiver and said first and second trains of pulses have respective recurrence rates equal to an integral multiple of said line-scanning rate and an integral submultiple of twice said line-scanning rate.

Claim 10

Test signal-generating apparatus for producing test patterns for a television receiver of the type employing a pair of signal-receiving terminals, an image-reproducing device, means for controlling the brightness of images produced on said device and scanning apparatus for scanning said device in first and second directions at respective first and second recurrence rates, said generating apparatus comprising means for deriving synchronizing signals at said first recurrence rate from said scanning apparatus, pulse-generating means responsive to said synchronizing signals for producing first and second trains of pulses having respective recurrence rates equal to integral multiples of said first and second recurrence rates, and switching means coupled to said pulse-generating means and between said pair of signal-receiving terminals for producIng an input signal to said receiver in response to pulses produced by said generating means, said input signal corresponding to image brightness level greater than maximum image brightness components of a received broadcast signal.

Claim 11

Test signal-generating apparatus for producing test patterns for a television receiver of the type employing a pair of signal-receiving terminals, an image-reproducing device, means for controlling the brightness of images produced on said device and scanning apparatus for scanning said device in first and second directions at respective first and second recurrence rates, said generating apparatus comprising means for deriving synchronizing signals at said first recurrence rate from said scanning apparatus, pulse-generating means responsive to said synchronizing signals for producing first and second trains of pulses having respective recurrence rates equal to integral multiples of said first and second recurrence rates, and switching means coupled to said pulse-generating means and between said pair of signal-receiving terminals for producIng an input signal to said receiver in response to pulses produced by said generating means, said input signal corresponding to image brightness level greater than maximum image brightness components of a received broadcast signal.