A controller for controlling a transceiver having a laser transmitter and a photodiode receiver. The multi-point video conference system includes a softswitch, an application server and terminals. Then, using bit error rate distribution, multivalue voltage along the first transition is determined. The double-layered strap forms a folded end and an open end, the folded end is connected with the pin and is wrapped around the pin, and the open end is separated into two portions which pass at the opening notch and are respectively connected to the body.