Disclosed are fused heterotricyclic compounds of the following formula I,or an enantiomer, diastereomer, tautomer or pharmaceutically acceptable salt thereof, wherein one of A ring or C ring is a 5-7 membered unsaturated heterocyclic ring. Signals are spread in a continuous spectrum by a spread spectrum signal, such as a direct sequence spread spectrum signal. The other housing is connected with a source of inflation fluid. When the programmable logic deviceunit is used for an encryptingdecrypting circuit, an encryptingdecrypting system that can flexibly change an algorithm at high speed can be accomplished. Apparatus for administering medical gases also includes a housing, a cassette associated with the housing containing at least one compressed gas cartridge preferably containing at least an amount of the medical gas substantially as required for a single dose and a patient supply interface to provide the medical gas to the patient. The interval can also be gravel packed in a single operation.