Abstract: A power supply for a television deflection apparatus is turned-on by a user initiated turn-on command. A fault detection circuit samples a voltage derived from the deflection circuit at the end of a predetermined interval that follows the turn-on command. The fault detection circuit issues a turn-off command to immediately shutdown the power supply, if such voltage is below a predetermined level indicative of a fault condition.

Abstract: In a power-up mode, the power supply of a television receiver generates the normal operating level of an energizing voltage. An overload detector generates a first control signal to shutdown the power supply and remove the energizing voltage when an overload condition occurs. A control circuit periodically samples the level of the energizing voltage. When the level is lower than normal, the control circuit generates a second control signal that maintains the power supply in the shut-down mode so as to prevent the power supply from attempting to restart. A third control signal inhibits the generation of the second control signal when an input alternating current voltage that supplies the power to the power supply suffers a voltage drop or blackout for only a short duration.

Abstract: In a battery operated, remote transmitter for a consumer instrument, a microprocessor controls operation of the transmitter. The collector current path of an on-off transistor is coupled between the battery and a voltage supply terminal of the microprocessor. To power up the microprocessor, a keyboard switch in the transmitter is depressed to activate a separate latch that is coupled to the base of the on-off transistor. Base current flows to the latch to turn on the transistor and apply the battery voltage to the voltage supply terminal of the microprocessor. After completion of the transmitter signaling, the microprocessor switches an output port to the ground state. The output port is coupled to a control terminal of the latch and bypasses holding current from a portion of the latch to initiate the regenerative deactivation of the latch. With the latch deactivated, conduction of the on-off transistor is cut off.

Abstract: A signal seeking tuning control system of a television receiver is first caused to operate in a first mode to search a frequency range surrounding a selected channel in accordance with predetermined conditions of a picture synchronization signal, and thereafter caused to operate in a second mode to search essentially the same frequency range but this time in response to predetermined conditions of an automatic fine tuning signal.

Abstract: A detector for determining the validity of a composite synchronization signal to indicate the presence of a picture carrier includes two threshold comparators set just below and just above the maximum and minimum amplitude excursions, respectively, of the synchronization pulses. The output pulses of the threshold comparators are counted during a reference interval to determine if the frequency of the synchronization pulses is correct. Due to the threshold comparators, noise transients are detected and counted so as to cause an incorrect frequency indication. In addition, reference pulses are counted during the duration of the output pulses generated by one of the threshold comparators to determine if the width of the synchronization pulses is correct. The number of incorrect counts of the frequency or width is counted during a measurement interval. If the number of incorrect counts exceeds a predetermined limit, the composite synchronization signal is not a valid one.

Abstract: In a phase locked loop PLL tuning control system for a voltage controlled local oscillator of the type wherein an automatic fine tuning voltage is selectively applied to the local oscillator after a PLL configuration has obtained lock at the nominal frequency value for the selected channel so as to accommodate frequency translated RF carriers, a circuit selectively activated by the average level of composite synchronization pulses indicative of improper tuning clamps the AFT voltage at a predetermined level. The predetermined level is selected to force the local oscillator frequency to be driven to an offset value at which an offset detector causes reinitiation of PLL control at discrete frequency step from the nominal value for the selected channel.

Abstract: A signal seeking tuning system of a television receiver includes a composite synchronization detector which generates a logic "0" when various parameters of the composite synchronization signal is correct and a logic "1" when they are incorrect as the local oscillator frequency is being decreased. After a transition detector determines when a transition from a "0" to "1" occurs, indicating the location of a picture carrier, the frequency of the local oscillator is stopped from changing.