Abstract: A system is disclosed for utilizing command buffers in a microprocessor controlled electronic code keyer for storing, rather than text to be transmitted, command strings for keyer operation. The command string is defined by a series of keypad closures for selecting a sequence of text buffers to be transmitted. In addition, the command buffers may be used during automatic text transmission to selectively change keyer parameters such as the speed of character transmission, inter-character and inter-word spacing, dot-to-dash-to-space ratio, or the number of times the contents of a text buffer will be automatically repeated. The use of text and command buffers permits the formation of essentially errorless Morse code transmissions, substantially enhances keyer operating and makes more efficient use of available memory.

Abstract: A mode decision controller is described for actuating a conventional chrominance bandwith enhancement scheme in a color television receiver. A video signal detected by the receiver typically includes a relatively wide band luminance element and a relatively narrow band chrominance element, each of which are processed by the enhancement scheme to develop their first derivatives for use in enhancing the bandwith of the chrominance element. Either of these derivatives may be used as an input to the mode decision controller. The selected derivative is applied to a filter for removing components therefrom which extend above a given frequency range, thereby developing a frequency-limited output signal whose time domain exceeds the time domain of the selected first derivative. A signal processor receives the frequency-limited output signal and compresses its time domain to develop a control signal whose time domain is substantially equivalent to the time domain of the selected first derivative.

Abstract: An electronic switch is provided for use in a battery-powered portable television receiver which eliminates power supply current drain when the television receiver is turned off. Coupled transistors are rendered conductive by means of either a clock or a manually switched input signal to provide a direct voltage battery output to television receiver circuitry. Also disclosed in an electronic switch combination for selectively controlling the audio output for the entire television receiver either manually or automatically.

Abstract: Video display distortion in a television receiver introduced by input voltage excursions is compensated for by a voltage regulation circuit which tracks the changing input line voltage while automatically switching to an active filter mode once the line voltage has decreased to a predetermined level. This permits the removal of AC transients from the fluctuating input signal and avoids display degradation resulting therefrom.

Abstract: Apparatus for generating an output signal having a frequency and duty cycle controllable in response to a pair of binary control words. The apparatus includes a pair of counters which are alternately enabled for counting high frequency clock pulses for respective time durations determined according to the two binary control words. A bi-stable device is controlled by the counters for developing the output signal which alternates between two levels for time durations corresponding to the time periods during which the two counters are enabled. The frequency and duty cycle of the output signal are therefore controllable by suitably adjusting the values of the two binary control words.

Abstract: A waveform generator for an electronic musical instrument comprises a signal generator (10) developing a binary signal sequentially increasing and decreasing in value at a selected rate and a memory (26) storing a plurality of parameter instructions at respective memory addresses, each memory address corresponding to a continuous group of values of the binary signal. An addressing circuit (24) addresses each memory address in response to the binary signal assuming a value within the group of values corresponding thereto. The binary signal is processed with the addressed parameter instructions in an arithmetic circuit (22,40) for developing a linear piecewise approximation of a desired waveform signal.

Abstract: A circuit for generating alternating repeat keying signals in an electronic keyboard musical instrument includes a clock, a logic circuit responsive to the keys of the instrument and to the clock for producing an alternating sequence of logic signals corresponding to each of the keys, the phase of the sequence corresponding to each undepressed key being the same as the phase of the sequence corresponding to the previous key and the phase of the sequence corresponding to each depressed key being opposite that of the phase of the sequence corresponding to the previous key and a plurality of output gates each developing a keying signal in response to the depression of a respective one of the keys and the logic signals of the corresponding sequence assuming a predetermined state.

Abstract: A sample and hold detector is described which preferably includes a differential amplifier, a current mirror and a storage capacitor which is charged and discharged to the voltage level of an electrical input signal during appropriate sampling intervals. The differential amplifier receives the electrical input signal as one input and the capacitor voltage as a second input for generating, at first and second differential amplifier output ports, currents which are a function of the voltage difference between its inputs. To charge and discharge the capacitor, the latter is coupled to the differential amplifier's second output port via a current path, and the current mirror is coupled between the output ports of the differential amplifier for sourcing to the second output port a predetermined percentage of differential amplifier current generated at the first output port.

Abstract: An easily installed thermal coupler inserted in the extruded section of a heat sink on which a transistor amplifier is mounted and positioned on a circuit board in thermal contact with diode biasing means coupled to the transistor amplifier. By thus thermally coupling the biasing means with the amplifier in a self-correcting, negative feedback loop, stable transistor operation is achieved and thermal runaway prevented. Employing a unitized metallic heat conducting member having a base plate including connecting studs for circuit board mounting and an upright member extending therefrom, the heat coupler may be used as either a heat sink or heat transfer device in carrying heat either out of or into the circuit board.

Abstract: A television receiver includes a frequency synthesizer phase lock loop operated in a time multiplexed manner to provide two tuning signals for tuning a received television signal. The two tuning signals are developed at the outputs of first and second voltage controlled local oscillators alternately operated in response to a phase detector which is reset at the beginning of each alternate operation.

Abstract: A color demodulation and comb filtering system is described for use in a color television receiver. The system includes a pair of charge coupled devices (CCD's) which each receive a filtered video signal and which develop outputs which are delayed, one from the other, by one horizontal line interval. Both devices are clocked at the color subcarrier frequency to develop outputs which include demodulated color and luminance components. The outputs of the two CCD's are combined in a summer, the output of which includes demodulated color components from which luminance components are eliminated.

Abstract: A service switch arrangement for a color television receiver having a low level matrixing system developing red, blue and green color signals includes a service switch having a normal position and a service position. In the normal position of the switch, a video output amplifier is enabled for coupling the red, blue and green color signals to the electron gun cathode elements of a color cathode ray tube. In the service position of the switch, the video output amplifier is disabled while an independently generated DC control voltage is coupled to the electron gun cathode elements for facilitating adjustment of the cut-off points of the cathode elements.

Abstract: An AFC circuit for a television system having stereophonic sound is disclosed. In response to a channel change, which causes a significant change in the level of the AFC error signal, the error signal is coupled substantially without modification to the local oscillator control terminal and the sound is muted. After an interval sufficient to permit frequency lock to be achieved the error signal is then coupled to the oscillator through a low pass filter and the muting operation is terminated.

Abstract: A CCD comb filter and color demodulation system is described for use in a color television receiver. The system includes a CCD comb filter receiving a video signal having interleaved luminance and color components, the latter components including a color subcarrier at a nominal frequency. Preferably, the comb filter includes but two CCD devices which receive the input video signal and apply their sampled outputs to a summer to develop combed luminance components and combed color components which occupy different frequency bands. The combed color components include a color subcarrier and sidebands which are translated upward in frequency by a given multiple of the nominal subcarrier frequency. The latter components are applied to a pair of CCD output filters which are clocked to sample the color components at the given multiple of the nominal subcarrier frequency for developing baseband demodulated color signals.

Abstract: A television receiver is disclosed for selectively displaying either a 525 line NTSC video signal or a 625 line European teletext or Viewdata signal. The receiver includes two vertical countdown circuits: a 525 line countdown circuit for use in generating an NTSC type raster, and a 625 line countdown circuit for use in generating a 625 line raster. Switch means are provided for selecting between the two signals generated by the countdown circuits. The receiver CRT uses self-converging, in-line guns.

Abstract: A variable frequency oscillator for an AC power supply having programmable, multiple phase outputs comprises means including a rate multiplier for generating a clock signal having a selectively controllable frequency and one or more AC signal producing stages responsive thereto. Each AC signal producing stage includes a memory storing a quarter-cycle sinusoidal waveform segment in amplitude sampled form and an address counter responsive to the clock signal for alternately addressing the memory in forward and reverse directions for producing a continuous sequence of half-cycle sinusoidal segments, an output circuit inverting every other one of the half-cycle segments.

Abstract: A system for preventing CRT phosphor burn in a multiple CRT projection type television system is disclosed. The absence of an electron beam deflection signal in the deflection yoke of a CRT is detected and used to provide a signal to CRT shutdown circuitry by means of an unbalanced transformer approach in which the various deflection yoke signals energize a plurality of primary transformer coils with a shutdown signal provided by the transformer secondary when a primary coil flux unbalance occurs.

Abstract: A luminance signal processing circuit for a television receiver comprises means for separating a full bandwidth luminance signal into a low pass component and first and second derivative components of the low pass component. A differential amplifier is responsive to the component voltage signals for developing first and second current mode signals representing in phase and 180.degree. out of phase combinations of the low pass and second derivative components. The levels of the second derivative components of the first and second current mode signals are selectively adjusted by a peaking signal processor for developing related third and fourth current mode signals whose amplitudes are also selectively adjusted by a picture signal processor for developing an output luminance voltage having selectively controlled contrast and peaking components.

Abstract: A programmable electronic musical synthesizer includes a memory controlling a plurality of parameter circuits according to a selected group of stored parameter signals for producing a desired timbre of sound. A memory override system is responsive to manual operation of each of a plurality of control knobs for overriding a corresponding stored parameter signal and coupling an externally derived input signal to the associated parameter circuit. The memory override system thereby conveniently enables one or more selected parameter circuits of the synthesizer to be manually controlled by a performer while the other parameter circuits are simultaneously controlled from memory.

Abstract: An envelope is imposed on a sequence of binary waveform samples representing a musical waveform signal by repetitively summing selected ones of a group of scaled representations of each of the waveform samples of the form A/2.sup.m, A/2.sup.m+1 . . . A/2.sup.m+p, where A represents the magnitude of the waveform sample, p is a predetermined integer, and m is an integer changing by a factor of unity each time a predetermined number of the groups have been developed. The sum of each group of scaled representations differs from the sum of the preceding group by the factor A/2.sup.m+p whereby a staircase signal is produced amplitude modulating the musical waveform signal, the step size of the staircase signal charging each time said predetermined number of groups have been developed.