Abstract: A circuit including emitter-coupled transistors improves the symmetry of an applied square wave. A limiter in the collector circuit limits the paraphase output voltage excursion. Changes in energizing voltage affect the current in the limiter and cause incremental changes in the output duty cycle. A compensator includes a voltage divider coupled between the output terminals for producing a control voltage related to the output signal amplitude. The control voltage controls a current source coupled to joined emitters for creating an offsetting current through the limiter.

Abstract: A balanced modulator or mixer is used for modulating components of a chrominance signal onto a subcarrier to generate double-sideband suppressed-carrier amplitude-modulated signals. The video component is applied to a phase splitter which produces two antiphase baseband video signals, which in turn are applied to modulator switches driven in antiphase at the carrier rate for producing the DSB SC signal at a common output terminal. For reducing residual carrier output resulting from unbalance of the video during black level, a sample-and-hold circuit is coupled to each output of the phase splitter and is gated during black level. A differential amplifier compares the sampled signals and reduces the unbalance in a feedback manner to eliminate residual subcarrier during black level.

Abstract: A feedback amplifier is configured as a contrast compressor for video signals including a reference blanking level. A feedback resistance is divided into two resistors coupled at a juncture. Contrast compression is accomplished by a diode coupled to the juncture and to a voltage source which may be adjusted to vary the point of onset of compression. The diode current perturbs the operating point of the amplifier, thereby producing a condition in which the blanking level at the output is other than zero volts. This is undesirable as it may affect following circuits adversely or require further setup. A clamp is coupled to the inverting input terminal for offsetting the perturbation of the amplifier operating point caused by the diode current.

Abstract: A synchronizing apparatus for compensating for cable length changes between a remote color television camera and a local control point is described. The color camera is of the type adapted to receive a "gen-lock" type reference signal for synchronization. The apparatus is responsive to the "gen-lock" signal and the signal from the television camera for generating a "gen-lock" type signal phase advanced to compensate for cable delays.

Abstract: A remotely controlled chroma key soft edger is described for use with an analog switcher. The keying signal is a low passed filtered and differentially summed with substantially an unfiltered keying signal and the resultant high frequency components are summed with the low pass filtered signal. The gain of the peaking signal is remotely controlled to adjust the summed rise time of the keying signal.

Abstract: A remotely controlled chroma keyer is provided which is responsive to the red, green and blue signals from a video source such as a color camera for providing color difference signals. A signal processing system using quadrant multipliers is used for summing and differencing these color difference signals which when applied to a non-additive mixer select a particular color. The color selection is determined by control voltages applied to the multipliers.

Abstract: A cable equalizer is provided for automatically compensating a signal for cable attenuation as the length of the cable is varied. The circuit detects changes in a reference signal that is inserted in the signal being transmitted over the cable. Any deviation of the reference signal from its normal state at the receiving end of the cable causes the addition of a correction signal to the signal being transmitted so as to compensate the signal for the cable attenuation.