Abstract: A controlled return path monitoring system is used in combination with an electrosurgical generator unit employing an active electrode for performing electrosurgery. The system includes internal electrode which is disposed, in use, within the body of a patient in proximity to the active electrode and is electrically connected to the electrosurgical generator unit so as to provide a preferred current return path back to the electrosurgical generator unit, and an external electrode which is disposed, in use, on the body of the patient and is electrically connected to the electrosurgical generator unit so as to provide a safety current return path back to the electrosurgical generator unit. A detector monitors the return current flow from the two electrodes back to the electrosurgical generator unit and controls the unit in accordance with the monitored return current flow, e.g., shuts off the unit when the flow exceeds a predetermined level.

Abstract: A trocar assembly includes an elongate trocar device and a surrounding cannula. The trocar device incorporates an electrosurgical cutting element which is used to make a guide hole for the cannula and thus enables the remainder of the trocar assembly to enlarge the puncture. An electronic control circuit senses the current flow to the cutting element and, when the trocar device breaks through the wall of the organ being cut, this circuit cuts off the connection to the associated electrosurgical generator. Further control circuitry prevents a surgeon from resuming electrosurgery until a predetermined time period has elapsed. Multiple trocars of different diameters are provided for the same assembly.

Abstract: A device is provided for use with a medical instrument including a tip which is designed to penetrate the wall of an internal cavity (e.g., the abdomen) of a patient, for detecting when that tip penetrates through the wall. The device includes a source of a medium frequency detection signal and circuitry for coupling the signal to the tip of the medical instrument. The circuitry includes a transformer forming a high Q resonant circuit having an initial value of Q when the medical instrument is not in use. A return path for the signal provides that, in use of the instrument, a circuit is completed through the resonant circuit such that when the tip contacts patient tissue the initial Q of the resonant circuit changes and when the tip penetrates through the patient tissue of the Q of the circuit is restored to the initial value thereon.

Abstract: A trocar assembly includes an elongate trocar device and a surrounding cannula. The trocar device incorporates an electrosurgical cutting element which is used to make a guide hole for the cannula and thus enables the remainder of the trocar assembly to enlarge the puncture. The cutting element comprises a bi-polar electrode assembly. An electronic control circuit senses the current flow to the cutting element and, when the trocar device breaks through the wall of the body cavity being cut into, this circuit cuts off the connection to the associated electrosurgical generator. Further control circuitry prevents a surgeon from resuming electrosurgery until a predetermined time period has elapsed. Multiple trocars of different diameters are provided for the same assembly.

Abstract: A binary-coded-decimal to binary converter employs a selection network to which the binary coded decimal digits are applied, the digits being selected in pairs of increasing order of decimal denominational significance to be passed to the address lines of a pair of memory elements, the locations of which contain the binary terms equivalent to the decimal digits from which the particular location address is derived. In order to increase the effective utilization of the memory elements, the binary code components specifying at least one of the decimal digits are manipulated by the selection network, for example by conversion to complementary form, before being applied to the address lines.