Abstract: An electrosurgical unit for producing a modulated oscillating signal for coagulation procedures and an unmodulated oscillating signal for cutting procedures. The unit includes a four arm bridge rectifier interconnected directly to the line voltage. A first pair of opposing diagonal terminals on the rectifier is connected directly to the line voltage. A cutting signal is obtained from the other pair of diagonal terminals, and a coagulation signal is obtained across one arm of the bridge rectifier. An oscillator tank coil provides the necessary RF isolation output. A switch selectively interconnects either the coagulation signal output from the bridge rectifier, or the cutting signal output from the bridge rectifier, to the oscillator. The output is taken across the tank circuit from the RF oscillator and applied to a patient through a handpiece. Through the use of high voltage transistors in the circuit, high efficiency is obtained by eliminating the input transformer of the prior art.

Abstract: An electrosurge generator, which is energized by a power supply to produce n output voltage of a desired level, includes a failsafe system at its output to prevent any excessive high DC voltage output which may result from a failure in the electrosurge generator. The failsafe system has a detection element coupled to the output of the electrosurge generator which detects any output above a predetermined threshold. A switching circuit is activated by the detection element. The switching circuit is connected across the power supply, and when activated, removes the power supplied from the power supply to the electrosurge generator.

Abstract: An electrosurgical unit which provides a voltage output to a load. An oscator in the unit produces the output of a given frequency. A switching circuit coupled to the oscillator provides an unmodulated RF carrier from the oscillator for use in cutting procedures and a pulse modulated RF voltage from the oscillator for use in coagulation procedures. A feedback circuit is coupled from the output to the input of the oscillator to maintain the output voltage level from the unit at a substantially constant value independent of the load.

Abstract: An electrosurgical unit for use in tissue cutting or coagulation procedur A vacuum tube oscillator operating in push-pull relationship generates RF oscillations which are extracted across a balanced coil transformer, the secondary of which is ungrounded. Forceps are provided to be connected across the output of the transformer for producing an isolated voltage for use in sealing off bleeding blood vessels. A handpiece is also provided for connection across the transformer output for selectively producing a cutting voltage or a coagulation voltage. An intensity control circuit is capable of connection in the power supply to control the output voltage. A pulse modulation unit is capable of being connected at the input of the oscillator to control the "on" time of the oscillator.

Abstract: A casting machine including a control circuit which automatically controls ts operation. The casting machine includes a casting chamber which supports an alloy filled open-ended container whose open end faces the sprue hole of an investment casting ring. The control circuit couples a vacuum to the casting chamber while maintaining the casting chamber in its initial upright position. After a first timing interval, the chamber is inverted and the vacuum is decoupled from the casting chamber, and compressed air is applied to the casting chamber. After a second subsequent time interval the casting chamber is automatically returned to its initial upright position, the action of which causes the casting chamber to be automatically vented to the atmosphere.