SA: PNP HF transistor SB: PNP AF transistor SC: NPN HF transistor SD: NPN AF transistor SE: Diodes SF: Thyristors SG: Gunn devices SH: UJT SJ: P-channel FET/MOSFET SK: N-channel FET/MOSFET SM: Triac SQ: LED SR: Rectifier SS: Signal diodes ST: A