A slotted upper track has double-thick sidewalls through which the slots extend. The input voltage is applied between the gate and drain and the output is taken between the source and drain. When the polling request is present, the network facsimile apparatus transmits the request file data corresponding to the request file number to the data receiving station. A surfaceunderside judging device is further provided, and a different process can be executed based on a result of a surfaceunderside judgement. The invention is also directed to the use of sulfur-containing amino acids or derivatives thereof in the microbial leaching of sulfidic materials, particularly in pyrite leaching. A systemmethod for providing an optically triggered bidirectional circuit breaker comprising common source JFETs and two photodetectors is alternatively provided.