A method and apparatus which provides a pressure sensor andor temperature sensor connected to the low pressure side of a refrigeration system, or the discharge line of a scroll compressor. Each subscriber terminal includes a photo-detector and one or more sources of modulated radiation. Test results are reported in a form that is expected or acceptable by the framework. The strumming mechanism provides cyclic motion and speed control to create pleasant and variable rhythm from the mounted guitar. The VCSEL also includes a reflective layer and a light emitting layer disposed between the grating layer and the reflector, in which the sub-wavelength grating and the reflector form a resonant cavity. The fourth control is to perform an authentication with regard to the recording medium in reference to the first and second data lines.