The present invention aims at providing an optical amplification apparatus for improving noise characteristics by controlling an amplification operation by assuming a noise figure of the overall apparatus and by taking influences of noise light due to Raman amplification into consideration, and a controlling method of the optical amplification apparatus. A particular use of the invention is a safety mechanism to hold the passenger-side door open while a disabled passenger is assisted in exiting the vehicle without the care-giving individual having to hold the door open or having the door slam shut on the disabled person. The wrench’s hydraulic cylinder rotates the wrench head upon actuation. Headphone assemblies may comprise two speaker assemblies and a headband configured for removable attachment to the speaker assemblies. Removing the base and flexible joint of the sheath device from the body of the sheath device leaves an air-impermeable dressing on the patient’s chest. The measuring apparatus can measure a micro difference or variation of the electric conductivity between a plurality of measuring points different in position or time with high reliability, accuracy and sensitivity.