Abstract: A method and apparatus are shown for generating and transmitting very short and widely separated high frequency sine-wave pulses of electromagnetic energy into space. A transistor, a charging capacitor, and an inductor are coupled into a first series loop path to form a discharge circuit. A bias voltage source, the same charging capacitor, and a charging resistor are coupled into a second series loop path to form a recharging circuit. The bias voltage source is selected to be capable of biasing the forward conduction path of the transistor near its breakdown condition. An original information signal is sampled upon each occurrence of a periodic reference signal, and the transistor is then triggered into its breakdown or avalanche mode. The starting times of successive transmitted pulses are modified in accordance with a pulse position modulation protocol.

Abstract: An everting tube device for introducing an elongated tool into a body cavity through a body opening for diagnostic or other purposes comprises an elongated housing containing a folded evertable flexible tube through which an elongated tool, such as a fiber optic bundle, sealingly extends. The flexible tube can be everted from the housing by applying fluid pressure to the housing interior, and the eversion of the tube carries the tool along with it at twice the rate. The tool can be retracted by applying vacuum to the housing interior which draws the tube away from the tool. The alternate use of pressure and vacuum, along with the intermediate steps of manually retracting the tool, result in projecting the tool and tube into the appropriate cavity at substantially the same rate. When the tool used is a fiber optic bundle, it provides a means of continuously viewing the path of travel immediately ahead of the advancing tube.