So spark transmitters could not transmit sound, and instead transmitted information by radiotelegraphy. However, in the upstream channel, ONUs can not transmit optical data signal in CM. In an emergency, submarines can transmit a signal to other ships. Both versions can transmit on either frequency. Every timeslot, nodes can transmit data to others. In full duplex operation, both stations may transmit simultaneously. Besides, hospitals must transmit discharge summaries to other facilities electronically. Monitoring stations usually transmit data back by terrestrial radio, although occasionally satellite systems are used. The replication techniques are somewhat dependent upon the media used to transmit the data. However, cable companies do not always reliably transmit PSIP information. These segments can either transmit or block light. Usually, in power systems, transformers transmit power simultaneously, no charge! Crows cannot transmit the virus to humans directly. It could instantly transmit pictures via cell phone telecommunication. Many materials will transmit some wavelengths while blocking others.