... Transceiver 20KM 2CH Video, 1CH Backward or Bi-directional Semiduplex RS485 Data 3 Levels Lightning Proof, Dual Powe 2CH Video Optical ... special note, are 10bit, 20KM distance,single mode FC fiber connector, single fiber bi-directional transmission.6, RS232, RS485,RS422, etc Supportable Optical Transceiver