Zenith Radio Corporation

Warwick Electronics Inc.

William R Weissmueller, Jr

A method and electronic circuit are described for generating a sawtooth waveform for vertical deflection of a television receiver's cathode ray tube. The method is effected by a circuit which includes a single capacitor which is charged to develop the ramp portion of the sawtooth. In response to a vertical sync pulse, the circuit discharges the capacitor and compares the capacitor's discharge voltage to a predetermined threshold voltage. When the latter two voltages are substantially equal to each other, discharge of the capacitor is discontinued, thus generating a sawtooth waveform across the capacitor. The capacitor begins charging again to form another ramp voltage and is discharged on receipt of the next vertical sync pulse. The charge and discharge of the capacitor repeats as successive vertical sync pulses are received.

Sawtooth waveform generation for a television receiver

An integratable vertical sync separator is described for use in a television receiver. The preferred embodiment includes an integrated capacitor which is charged and alternately discharged by current sources in response to composite sync pulses such that the capacitor develops a relatively high level voltage when vertical sync pulses are received. The voltage developed by the capacitor is sensed by a peak detector for developing a vertical sync output pulse and for producing a feedback signal indicative of the amplitude of the relatively high level voltage on the capacitor. The feedback signal is applied to the current sources which are conditioned to vary the charge and discharge rates of the capacitor for improved performance in sub-standard signal conditions.

Integratable vertical sync separator

A two-mode digital vertical synchronization system is described for controlling the phase synchronization of vertical scan in a television receiver. In one mode, the system searches for incoming vertical sync pulses which occur during a wide sync 'window'. Sync pulses received during that window are utilized to initiate vertical scan. When the received sync pulses are in time-coincidence with an internal control signal generated at a standard line/frame rate, the system switches to a narrow window mode of operation. Vertical sync pulses received during a narrow sync window continue to initiate vertical scan. When a lack of time-coincidence between received vertical sync pulses and the control signal occurs for a predetermined interval, the system reverts to its wide window mode. Preferably, the locally generated control signal has a time duration sufficient to permit detection of coincidence between itself and a typical non-standard vertical sync pulse to hold the system in the narrow window mode, thus preventing oscillation between the narrow and wide window modes.

Vertical synchronization system

In a television receiver, a tuning voltage for a varactor tuner is generated by the actuated stage of a plural step neon lamp memory in which each memory stage corresponds to a different television channel. The memory stages are connected as a ring counter which is stepped sequentially by a two-speed oscillator having a fast scan for undesired channel representing stages, and a slow scan to maintain actuation for a short time period of selected memory stages which correspond to desired channels which are to be viewed. Each memory stage includes a potentiometer with a wiper adjusted to generate the tuning voltage. To preprogram the undesired channel representing stages, the potentiometers in the stages are adjusted to produce maximum voltage, which is detected by a threshold switch to cause the oscillator to rapidly step to the next memory stage. A counter detects when all memory stages have been scanned and then disables the oscillator thereby stopping the scanning to maintain selection of the original channel.

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Wildwood, IL, United States of America

William R Weissmueller, Jr