A method of forming an integrated circuit structure includes providing a chip; forming a static random access memory cell including a transistor on the chip; and forming a bias transistor configured to gate a power supply voltage provided to the SRAM cell on the chip. A part of a fringe of each of the first and second optical surfaces is substantially in a form of a circle whose center is on the optical axis is cut off by each of the first and second straight line portions. % and is Co or Fe, Y accounts for between about 20 at. The second switching system also includes subscriber line ports for receiving local voice signals and local data signals from subscribers.